Climate of the United States

The climate of the United States varies due to differences in latitude, and a range of geographic features, including mountains and deserts. Generally, on the mainland, the climate of the U.S. becomes warmer the further south one travels, and drier the further west, until one reaches the West Coast.

West of the 100th meridian, much of the U.S. has a cool to cold semi-arid climate in the interior upper western states, to warm to hot desert and semi-arid climates in the rest of the western and southwestern U.S. East of the 100th meridian, the climate is humid continental in northern areas (locations roughly above 40 north latitude), transitioning into a humid temperate climate from the Southern Plains and lower Midwest east to the Middle Atlantic states. A humid subtropical climate is found along and south of a mostly east-west line from the Virginia capes (north of the greater Norfolk area), westward to northern Oklahoma. Along the Atlantic seaboard, the humid subtropical climate zone extends southward into central Florida, such as the greater Orlando area. A Mediterranean climate prevails along most of the California coast, while southern Florida has a tropical climate, the warmest region on the US mainland.[1]

Higher-elevation areas of the Rocky Mountains, the Wasatch Range, Sierra Nevada, and Cascade Range are alpine. Coastal areas of Oregon and Washington have an oceanic climate. The state of Alaska, on the northwestern corner of the North American continent, is largely dominated by a subarctic climate, but with a subpolar oceanic climate in the southeast (Alaska Panhandle), southwestern peninsula and Aleutian Islands, and a polar climate in the north.

The primary drivers of weather in the contiguous United States are the seasonal change in the solar angle, the migration north/south of the subtropical highs, and the seasonal change in the position of the polar jet stream.

In the Northern Hemisphere summer, the subtropical high pressure systems move northward and closer to the United States mainland. In the Atlantic Ocean, the Bermuda High creates a south-southwest flow of warm, humid air over the southern, eastern and central United States - resulting in warm to hot temperatures, high humidity and occasional to frequent showers and/or thunderstorms. In the Northern Hemisphere summer, high pressure in the Pacific Ocean builds toward the California coast, resulting in a northwesterly airflow, creating the cool, dry, and stable weather conditions prevalent along the West Coast in summer.

In the Northern Hemisphere winter, the subtropical highs retreat southward. The polar jet stream (and associated conflict zone between cold, dry air masses from Canada and warm, moist air masses from the Gulf of Mexico) drops further southward into the United States - bringing more frequent periods of stormy weather, with rain, ice and snow, and much more variable temperatures, with rapid temperature rises and falls not uncommon. Areas in the southern U.S. (Florida, the Gulf Coast, the Desert Southwest, and southern California) however, often have more stable weather, as the polar jet stream's impact does not usually reach that far south.

Weather systems, be they high-pressure systems (anticyclones), low-pressure systems (cyclones) or fronts (boundaries between air masses of differing temperature, humidity and most commonly, both) are faster-moving and more intense in the winter/colder months than in the summer/warmer months, when the belt of lows and storms generally moves into southern Canada.

The Gulf of Alaska is the origination area of many storms that enter the United States. Such "North Pacific lows" enter the U.S. through the Pacific Northwest, then move eastward across the northern Rocky Mountains, northern Great Plains, upper Midwest, Great Lakes and New England states. Across the central states from late fall to spring, "Panhandle hook" storms move from the central Rockies into the Oklahoma/Texas panhandle areas, then northeast toward the Great Lakes. They generate unusually large temperature contrasts, and often bring copious Gulf moisture northward, resulting sometimes in cold conditions and possibly-heavy snow or ice north and west of the storm track, and warm conditions, heavy rains and potentially-severe thunderstorms south and east of the storm track - often simultaneously. Across the northern states in winter usually from Montana eastward, "Alberta clipper" storms track east and bring light to moderate snowfalls from Montana and the Dakotas across the upper Midwest and Great Lakes states to New England, and often, windy and severe Arctic outbreaks behind them. When winter-season Canadian cold air masses drop unusually far southward, "Gulf lows" can develop in or near the Gulf of Mexico, then track eastward or northeastward across the Southern states, or nearby Gulf or South Atlantic waters. They sometimes bring rain, but can bring snow or ice across the South, mostly in interior or northern areas.

In the cold season (generally November to March), most precipitation occurs in conjunction with organized low-pressure systems and associated fronts. In the summer, storms are much more localized, with short-duration thunderstorms common in many areas east of the 100th meridian and south of 40 latitude. In the warm season, storm systems affecting a large area are less frequent, and weather conditions are more solar {sun} controlled, with the greatest chance for thunderstorm and severe weather activity during peak heating hours, mostly between 3 PM and 9 PM local time. From May to August especially, often-overnight mesoscale-convective-system (MCS) thunderstorm complexes, usually associated with frontal activity, can deliver significant to flooding rainfall amounts from the Dakotas/Nebraska eastward across Iowa/Minnesota to the Great Lakes states. From late summer into fall (mostly August to October), tropical cyclones (hurricanes, tropical storms and tropical depressions) sometimes approach or cross the Gulf and Atlantic states, bringing high winds, heavy rainfall, and storm surges (often topped with battering waves) to coastal areas.

Record 1 day precipitation by USA county 1979 - 2011
Record one day precipitation by county between 1979 and 2011.
Average Annual High Temperature of the United States
A map of the average annual high temperatures in the United States.
US 50 states Köppen
Köppen climate types of the U.S. (The territories of the United States are not on the map)

Regional overview


The Southwest has a hot desert climate, at lower elevations. Cities like Phoenix, Las Vegas, Yuma, and Palm Springs have average highs over 100 °F (38 °C) during the summer months and lows in the 70s or even 80s. In winter, daily temperatures in the southwest are cooler with highs in the 50s and 60s F, and lows in the 40s F.

In Phoenix, Las Vegas and similar Southwestern desert areas, on average June is the driest month, after Pacific-originating winter storms have concluded and before the Southwestern summer "monsoon" begins. The Southwest and the Great Basin are affected by said monsoon from the Gulf of California from July–September. This results in some increase in humidity and cloud cover, bringing higher nighttime low temperatures and localized thunderstorms to the region, which can result in flash flooding. Further eastward in the desert Southwest (Tucson, AZ eastward toward El Paso, TX), winter-season precipitation decreases, while the summer monsoon increasingly provides a summer precipitation maximum. For example, El Paso and Albuquerque, NM have a pronounced July to September precipitation maximum. Still, drought has been frequent in the region, often lasting for periods of years or longer. Forest fires across the Western United States (especially the southwest) occur many years, and can be severe to extreme in especially hot, dry summer seasons.

Northern Arizona and New Mexico, central and northern Nevada and most of Utah (outside higher mountain areas) have a temperate semi-desert to desert climate, but with colder and snowier winters than in Phoenix and similar areas, and less-hot summers (as at Salt Lake City, Utah). Summer high temperatures often reach the 90s, but low temperatures drop into the low 60s and even 50s. As in other temperate desert climates, the dry air results in large differences (sometimes over 40 degrees) between daytime high and nighttime low temperatures. Precipitation, though scarce, often falls year-round, influenced both by summer thunderstorms brought by the Southwestern monsoon (primarily in southern areas), and by winter-season storms from the Pacific Ocean.

The coast of California has a Mediterranean climate. Daily high temperatures range from 70 to 80 °F (21 to 27 °C) in the summer to 50 to 65 °F (10 to 16 °C) in winter, with low temperatures from the 60 °F (16 °C)s in summer to the mid 40s F in winter. Like most Mediterranean climates, much of coastal California has a wet winter and dry summer. Early summers can often bring cool, overcast weather (fog and low stratus clouds) to coastal California. As such, the warmest summer weather is delayed until August, even September in many areas of the California coast; on average, September is the warmest month in San Francisco, CA. Upwelling of cold Pacific waters also contributes to the frequent cool spring and early summer weather in coastal California. In California's inland river valleys (Bakersfield, Sacramento areas), the wet-winter, dry-summer pattern remains, but winters are cooler and more prone to occasional frost or freeze, while summers are much hotter, with blazing sunshine and daytime high temperatures not uncommonly in the 90s °F to over 100 °F (38 °C).

Gulf Coast/Lower Mississippi Valley/South Atlantic states

The Gulf and South Atlantic states have a humid subtropical climate with mostly mild winters and hot, humid summers. Most of the Florida peninsula including Tampa and Jacksonville, along with other coastal cities like Houston, New Orleans, Savannah, GA, Charleston, SC and Wilmington, NC all have average summer highs from near 90 to the lower 90s F, and lows generally from 70 to 75 °F (21 to 24 °C); combined with moist tropical air, this creates the sultry summer weather conditions that prevail here.

In the interior South, in cities like Raleigh, NC, Atlanta, Birmingham, AL, Nashville, TN and Jackson, average summer highs and lows are similar to coastal areas, while some areas of interior eastern and central Texas (i.e. Dallas, Austin and San Antonio areas) have average daily highs in the mid to upper 90s F. In winter, average daily high temperatures range from the 40 °F (4 °C)s (upper South: northern Arkansas, Kentucky and Virginia), to the 60 °F (16 °C)s along the Gulf Coast and South Atlantic coast (Charleston southward), with 70 °F (21 °C)s in central Florida and far southern Texas. Average daily lows in winter range from 20 °F (−7 °C)s north to 40 °F (4 °C)s along the Gulf and far South Atlantic coasts, with 50 °F (10 °C)s in Florida and coastal south Texas.

Much of the interior South (Tennessee, Kentucky and the northern Gulf states) has a winter or spring maximum in precipitation, with December, March or April typically the wettest month, and August to October the driest months - for example, at Birmingham, AL, Huntsville, AL, Tupelo, MS and Memphis, TN. From November to April, these areas commonly experience sharp conflicts between cold, dry air from Canada and warm, moist air from the Gulf of Mexico. These air-mass clashes often bring heavy winter and spring precipitation to the Mid-South. Given the tropical air masses, summer-season thunderstorms can occur throughout the South, but they are heavier and more frequent along the Gulf Coast, South Atlantic coast (Norfolk, VA area southward), and in peninsular Florida. Along most of the Gulf coast (i.e. New Orleans, LA, Mobile, AL and Pensacola, FL areas), and in South Atlantic coastal and sandhills areas (i.e. Columbia, SC, Fayetteville, NC, Raleigh, NC, Wilmington, NC, and Norfolk, VA), July and August are usually the wettest months, and precipitation is fairly evenly distributed the rest of the year. Primarily from August to early October, the coastal Gulf and South Atlantic states are susceptible to being struck by tropical weather systems (tropical depressions, tropical storms, and hurricanes). Even in winter, most precipitation falls as rain. However, occasionally frozen precipitation (snow, sleet and/or freezing rain) can occur (more commonly in interior and northern areas) when southerly-tracking storms throw Gulf or Atlantic moisture over cold air at ground level.

Southern Florida has a tropical climate, with all months having a mean temperature of higher than 65 °F (18 °C), a wet season from May through October, and a dry season from November through April. In cities like Fort Lauderdale, Miami, Key West, Naples, and Palm Beach average daily highs range from the mid 70 °F (21 °C)s in winter to near 90 °F (32-33 °C) in summer. Average overnight lows range from the upper 50 °F (10 °C)s in winter to the mid and upper 70 °F (21 °C)s in summer. Southern Florida is the warmest region of the U.S. mainland in winter.

Southern Plains/Lower Midwest/Middle East Coast

The region from the southern Plains, to the lower Midwest, eastward to the central East Coast (the New York City/coastal Connecticut region southward to Virginia) has a temperate climate with cool to cold winters and hot, humid summers. Daytime highs range from 80 to 90 °F (27 to 32 °C) in summer to 35 to 50 °F (2 to 10 °C) in winter. Lows range from the 60 °F (16 °C)s in summer to 25 to 35 °F (−4 to 2 °C) in winter. Cities in this region include Wichita, KS, St. Louis, MO, Springfield, IL, Indianapolis, IN, Columbus, OH, Pittsburgh, PA, Philadelphia, PA, Washington, D.C., Richmond, VA, New York City, NY, New Haven, CT, and Atlantic City, NJ. Precipitation is spread fairly evenly throughout the year, though as one travels from Indiana westward there is an increasingly prominent early-summer concentration, with a May maximum in northern Texas and Oklahoma, and a June maximum increasingly evident from (central/northern) Indiana westward to Kansas. As one travels from east to west across Texas, Oklahoma and Kansas, average annual precipitation steadily decreases. Far western Texas (El Paso area) is desert, and average annual precipitation is less than twenty inches (510 mm) in westernmost Kansas and the Oklahoma Panhandle, where the climate qualifies as semi-arid.

In the lower Midwest (and southern Plains states, especially), temperatures can rise or drop rapidly; winds can be extreme; and clashing air masses, including hot, dry air of Mexican and/or Southwestern origin, warm, moist air from the Gulf of Mexico and cold, dry air from Canada can spawn severe thunderstorms and tornadoes, particularly from April to June. The "dryline," separating hot, dry air of Mexican/Southwestern U.S. origin from warm, moist air from the Gulf of Mexico, often causes severe, occasionally violent, thunderstorms to fire in central and eastern Texas, Oklahoma and Kansas; these sometimes contribute toward the hailstorms and tornado outbreaks that the Southern Plains are well known for. Reflecting these air-mass conflicts, central Oklahoma, including the Oklahoma City and Moore-Norman areas, has the highest frequency of tornadoes per unit land area on planet Earth, with May the highest-risk month for tornadoes throughout "Tornado Alley," from northern Texas north-northeastward toward western and central Iowa.

Northern Great Plains/North-Central/Great Lakes/New England

The northern half of the Great Plains (Nebraska northward), northern Midwest, Great Lakes, and New England states have a humid continental climate. Here there are four distinct seasons, with warm to hot summers, and cold and often-snowy winters. Average daily high temperatures range from 10 °F (−12 °C)s (in North Dakota, and central and northern Minnesota) to 30 °F (−1 °C)s in winter to 70 to 80 °F (21 to 27 °C)s in summer, while overnight lows range from below 0 °F (−18 °C) in winter (in North Dakota and much of Minnesota) to 50 to 60 °F (10 to 16 °C)s in summer. In the New England states, precipitation is evenly distributed around the year, with a slight late fall-early winter (November–December) maximum along the New England coast from Boston, MA northward due to intense early-winter storms. In the Great Lakes states, cold Arctic air in winter crossing the relatively warmer lake waters can result in frequent and sometimes very heavy lake-effect snow, especially on the eastern and southern shores of the Great Lakes (for example, in western Michigan's Lower Peninsula and in the Buffalo, NY area). Cities in this area include Minneapolis, MN, Omaha, NE, Sioux Falls, SD, Fargo, ND, Chicago, IL, Cleveland, OH, Buffalo, NY, Albany, NY, Boston, MA, Concord, NH and Augusta, ME. As one travels from east to west across Nebraska, South Dakota and North Dakota, average annual precipitation steadily decreases, and the westernmost counties of these states have a semi-arid climate, with about or just over 15 inches of precipitation per year, on average (see climate data for Williston, ND, Rapid City, SD and Scottsbluff, NE).

In the upper Midwest and northern Plains states, temperatures may rise or fall rapidly, and winds (from warm-season thunderstorms or larger-scale low-pressure systems) can be strong to extreme. Here, air-mass conflicts primarily involve warm, moist air from the Gulf of Mexico, clashing with cool to cold, dry air from Canada, with only occasional intrusions of hot, dry air from the southwest. The conflicts between Canadian and Gulf air commonly produce severe thunderstorms (including hailstorms, especially on the western Plains) and tornadoes, particularly in May and June. In the northern Plains and North Central states generally, June is the year's wettest month on average, owing to maximum shower and thunderstorm activity. Also, June is the highest-risk month for severe weather throughout North Dakota, South Dakota, Minnesota, Iowa, Wisconsin and northern Illinois.

Pacific Northwest

The Pacific Northwest has an oceanic climate. The climate is wet and cool in autumn, winter, and spring, and stable and drier in the summer months, especially July and August. On average, the wettest month is typically November or December; the driest, July. In the summer months, average highs in cities like Seattle and Portland are from 70 to 75 °F (21 to 26 °C) with lows from 50 to 59 °F (10 to 15 °C), while in winter daily highs are from 40 to 45 °F (4 to 9 °C) and overnight lows from 30 to 38 °F (−1 to 4 °C).

In winter, the Pacific Northwest (especially coastal districts and other areas west, i.e. on the prevailing windward side, of the Olympic and Cascade mountain ranges), experiences a mostly overcast, wet and cool climate, but without severe cold like that found in the interior northern U.S. (i.e. Minnesota/North Dakota). At lower elevations, winter precipitation falls mostly as rain. However, snow does occur even at the lowest elevations, primarily when Pacific moisture interacts with cold air intruding into the Pacific Northwest from western Canada (i.e. Alberta and interior British Columbia). In Seattle, WA and Portland, OR, winter-season snowfall varies greatly; in Seattle, the average winter-season snowfall is about 7 inches. In January 1950 (the coldest month in Pacific Northwest history), Seattle received an all-time record 57 inches of snow;[2] that same month, Portland received 41 inches.[3][4] Summers in the Pacific Northwest are generally cool, especially along the coastline. The Great Basin and Columbia Plateau (the Intermontane Plateaus) are arid or semiarid regions, with high summer temperatures in the 90s to occasionally over 100 at lower elevations (e.g. at Boise, ID), with annual precipitation averaging less than 15 inches (380 mm) as a result of the rain shadow of the Sierra Nevada and Cascades. Both coastal and interior areas of Oregon and Washington, and southern Idaho, have a wet-winter, dry-summer precipitation pattern, but traveling eastward into Montana and Wyoming, this transitions progressively (for example, at Missoula, MT) toward relatively drier winters and a May and eventually June precipitation maximum, the latter characteristic of the Northern Plains and much of the upper Midwest (i.e. both Dakotas, Nebraska, Iowa and Minnesota).


See also: Climate of Alaska, Climate change in southeast Alaska

The climate in Juneau and the southeast panhandle is a mid-latitude oceanic climate[5] (Köppen Cfb). The climate in the extreme north of Alaska is what would be expected for an area north of the Arctic Circle — it is an Arctic climate (Köppen ET) with long, very cold winters and short, cool summers.[6] says the following: "The altitude above sea level influences the climate of a given area [in Alaska]. Lower elevations in interior Alaska, such as the Yukon Flats and the Tanana Valley experience extreme cold in the winter as well as high summertime temperatures."[7]

Hawaii and the U.S. territories

A view of Ofu beach on Ofu-Olosega in American Samoa

See also: Climate of Hawaii, Climate of Puerto Rico

Hawaii, American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, the U.S. Virgin Islands and the U.S. Minor Outlying Islands have tropical climates; all of these U.S. regions consist of island(s).[1] Though Hawaii is tropical, Hawaii has several different climates at different altitudes.

In 2015, the Wall Street Journal reported that U.S. territories such as Puerto Rico are the areas of the U.S. most vulnerable to climate change.[8]


Precipitation (whether by annual amount, annual distribution or characteristic[s]) varies significantly across the United States and its possessions. Late summer and fall extratropical cyclones bring a majority of the precipitation which falls across western, southern, and southeast Alaska annually. During the fall, winter, and spring, Pacific storm systems bring most of Hawaii and the western United States much of their precipitation. Most of Florida has a subtropical monsoon rainfall pattern (wet summer and dry winter).[9]

In the central and upper eastern United States, precipitation is evenly distributed throughout the year, although summer rainfall increases as one moves southeastward. Lake-effect snows add to precipitation potential downwind of the Great Lakes,[10] as well as Great Salt Lake and the Finger Lakes during the cold season. The average snow to liquid ratio across the contiguous United States is 13:1, meaning 13 inches (330 mm) of snow melts down to 1 inch (25 mm) of water.[11] The El Niño-Southern Oscillation affects the precipitation distribution, by altering rainfall patterns across the West, Midwest, the Southeast, and throughout the tropics.[12][13][14][15]

During the summer, the Southwest monsoon combined with Gulf of California and Gulf of Mexico moisture moving around the subtropical ridge in the Atlantic Ocean bring the promise of afternoon and evening thunderstorms to the southern tier of the country as well as the Great Plains.[16] Equatorward of the subtropical ridge, tropical cyclones enhance precipitation (mostly from August to October) across southern and eastern sections of the country, as well as Puerto Rico, the United States Virgin Islands, the Northern Mariana Islands, Guam, and American Samoa.[17] Over the top of the ridge, the jet stream brings a summer precipitation maximum to the Great Lakes. Large thunderstorm areas known as mesoscale convective complexes move through the Plains, Midwest, and Great Lakes during the warm season, contributing up to 10% of the annual precipitation to the region.[18]


Several different air masses affect the United States.

In northern Alaska, tundra and arctic conditions predominate, and the temperature has fallen as low as −80 °F (−62 °C).[19] On the other end of the spectrum, Death Valley, California once reached 134 °F (56.7 °C), officially the highest temperature ever recorded on Earth.[20]

On average, the mountains of the western states receive the highest levels of snowfall on Earth. The greatest annual snowfall level is at Mount Rainier in Washington, at 692 inches (1,758 cm); the record there was 1,122 inches (2,850 cm) in the winter of 1971–72. This record was broken by the Mt. Baker Ski Area in northwestern Washington which reported 1,140 inches (2,896 cm) of snowfall for the 1998-99 snowfall season. Other places with significant snowfall outside the Cascade Range are the Wasatch Range, near the Great Salt Lake and the Sierra Nevada, near Lake Tahoe.

Along the coastal mountain ranges in the Pacific Northwest, rainfall is greater than anywhere else in the continental U.S., with Quinault Ranger Station in Washington having an average of 137 inches (3,480 mm).[21] Hawaii receives even more, with 404 inches (10,262 mm) measured annually, on average, at the Big Bog, in Maui.[22] The Sonoran Desert in the southwest is home to the driest locale in the US. Yuma, Arizona, has an average of 2.63 inches (67 mm) of precipitation each year.[23]

Extreme highs

Month Temperature Date Location
January 98°F (37°C) January 5, 1997 Zapata, Zapata County, Texas
February 104°F (40°C) February 26, 1902 Fort Ringgold, Starr, Texas
March 108°F (42°C) March 14, 1902 and March 31, 1954 Rio Grande City, Starr, Texas
April 118°F (48°C) April 25, 1898 Volcano Springs, Imperial, California
May 122°F (50°C) May 1 and 30, 2000 Furnace Creek, Inyo, California
June 129°F (54°C) June 30, 2013 Furnace Creek, Inyo, California
July 134°F (57°C) July 10, 1913 Furnace Creek, Inyo, California
August 127°F (53°C) August 12, 1933 Furnace Creek, Inyo, California
September 126°F (52°C) September 2, 1950 Mecca, Riverside, California
October 117°F (47°C) October 5, 1917 Mecca, Riverside, California
November 105°F (41°C) November 12, 1906 Craftonville, San Bernardino, California
December 100°F (38°C) December 8, 1938 La Mesa, San Diego, California

Extreme lows

Month Temperature Date Location
January -80°F (-62°C) January 23, 1971 Prospect Creek, Yukon-Koyukuk, Alaska
February -75°F (-59°C) February 3, 1947 Tanacross, Southeast Fairbanks, Alaska
March -68°F (-56°C) March 1, 1971 Kobuk, Northwest Arctic, Alaska
April -50°F (-46°C) April 5, 1995 Umiat, North Slope, Alaska
May -25°F (-32°C) May 5, 1992 Chandalar Lake, Yukon-Koyukuk, Alaska
June -11°F (-24°C) June 28, 1971 Anaktuvuk, North Slope, Alaska
July 8°F (-13°C) July 20, 1967 Anaktuvuk, North Slope, Alaska
August 5°F (-15°C) August 15, 1997 Umiat, North Slope, Alaska
September -15°F (-26°C) September 20, 1983 Big Piney, Sublette County, Wyoming
October -48°F (-44°C) October 31, 1975 Clear Water, Denali, Alaska
November -62°F (-52°C) November 30, 1970 Prospect Creek, Yukon-Koyukuk, Alaska
December -72°F (-58°C) December 31, 1999 Chicken, Southeast Fairbanks, Alaska

Natural disasters and effects

Dimmitt Tornado1 - NOAA
A powerful tornado in Texas.
View of flooded New Orleans in the aftermath of Hurricane Katrina

Because of contrasting air masses, the Great Plains, the Midwest, and the southern United States have frequent severe thunderstorms and tornado outbreaks during both the spring and the summer. In central portions of the U.S., tornadoes are more common than anywhere else in the world.[26] They usually can touch down during the spring and the summer. The strip of land from north Texas north to Nebraska and east into Southern Michigan is known as Tornado Alley, where many houses have tornado shelters and where many towns have tornado sirens. Stretching across Mississippi and Alabama, Dixie Alley has experienced both tornadoes and violent thunderstorms, with peak tornado season coming on as early as February and waning by May. Florida also reports many tornadoes, but these rarely are very strong. The southern US has a second tornado season during the autumn. Generally, the area at greatest risk for tornadoes migrates northward from February to June, peaking in the Gulf States in February and March, the Ohio Valley and lower Midwest in April, southern and central Plains and central Midwest in May, and Northern Plains and upper Midwest (Dakotas, Minnesota, and Wisconsin) in June.

Both the Appalachian region and the Midwest experience the worst floods. Widespread severe flooding is rare. Some exceptions include the Great Mississippi Flood of 1927, the Great Flood of 1993, and widespread flooding and mudslides caused by the 1982–83 El Niño event in the western United States. Localized flooding can, however, occur anywhere. Mudslides from heavy rain can even cause problems in any mountainous areas, particularly in the Southwest. The narrow canyons of many mountain areas in the west and severe thunderstorm activity during the monsoon season in summer leads to sometimes devastating flash floods as well. On the other hand, Nor'easter snowstorms can bring activity to a halt in both the New England and Great Lakes regions.

In 2013, the US sustains $10 billion annually in damage from floods.[27]

The Southwest has the worst droughts; one is thought to have lasted over 500 years and to have decimated the Anasazi people.[28] Large stretches of desert shrub in the west can fuel the spreads of wildfires. Although severe drought is rare, it has occasionally caused some major problems, such as those during the Dust Bowl (1931–1942), which coincided with the Great Depression. Farmland failed throughout the Plains, entire regions were virtually depopulated, and dust storms ravaged the land. More recently, the western US experienced widespread drought from 1999 to 2004.

In terms of deaths from heatwaves, 7,415 losses occurred between 1999 and 2010, a mean of 618 per year. A disproportionate number of men, a full 68% of deaths, versus women have been affected. The highest yearly total of heat-related deaths during that time frame was in 1999. The lowest was in 2004.[29] In terms of deaths caused by waves of cold temperatures, the same gender inequality exists; 66% of hypothermia-related deaths in 2002 were of males. From 1979 to 2002, 16,555 deaths occurred due to exposure to excessive cold temperatures, a mean of 689 per year.[30]

See also


  1. ^ a b Chapter 6 - U.S. Tropical Forests: Caribbean and Western Pacific. Retrieved January 8, 2019.
  2. ^ "Just how bad was the winter of 1949-1950?".
  3. ^ "January snowstorm is among top 10 in Portland history".
  4. ^ "Portland, Oregon -- long-term cold and snow records and ice storms and silver thaws".
  5. ^ Juneau. Retrieved January 11, 2019.
  6. ^ Alaska Climate - Arctic. Retrieved January 11, 2019.
  7. ^ Retrieved January 11, 2019.
  8. ^ The Wall Street Journal. Why U.S. Territories Are Most Vulnerable to Climate Change. Kate Gordon. March 31, 2015. Retrieved January 9, 2019.
  9. ^ Norman W. Junker. West Coast Cold Season Heavy Rainfall Events. Retrieved on 2008-03-01.
  10. ^ Thomas W. Schmidlin. Climatic Summary of Snowfall and Snow Depth in the Ohio Snowbelt at Chardron. Retrieved on 2008-03-01.
  11. ^ Martin A. Baxter, Charles E. Graves, and James T. Moore. A Climatology of Snow-to-Liquid Ratio for the Contiguous United States. Retrieved on 2008-03-21.
  12. ^ John Monteverdi and Jan Null. WESTERN REGION TECHNICAL ATTACHMENT NO. 97-37 NOVEMBER 21, 1997: El Niño and California Precipitation. Retrieved on 2008-02-28.
  13. ^ Nathan Mantua. La Niña Impacts in the Pacific Northwest. Archived October 22, 2007, at the Wayback Machine Retrieved on 2008-02-29.
  14. ^ Southeast Climate Consortium. SECC Winter Climate Outlook. Archived March 4, 2008, at the Wayback Machine Retrieved on 2008-02-29.
  15. ^ Reuters. La Nina could mean dry summer in Midwest and Plains. Retrieved on 2008-02-29.
  16. ^ National Weather Service Forecast Office Flagstaff, Arizona. The Monsoon. Retrieved on 2008-02-28.
  17. ^ Roth, David M; Weather Prediction Center (January 7, 2013). "Maximum Rainfall caused by Tropical Cyclones and their Remnants Per State (1950–2012)". Tropical Cyclone Point Maxima. United States National Oceanic and Atmospheric Administration's National Weather Service. Retrieved March 15, 2013.
  18. ^ Walker S. Ashley, Thomas L. Mote, P. Grady Dixon, Sharon L. Trotter, Emily J. Powell, Joshua D. Durkee, and Andrew J. Grundstein. Distribution of Mesoscale Convective Complex Rainfall in the United States. Retrieved on 2008-03-02.
  19. ^ Williams, Jack Each state's low temperature record, USA Today, URL accessed 13 June 2006.
  20. ^ "World: Highest Temperature". World Weather / Climate Extremes Archive. Arizona State University. 2012. Archived from the original on January 4, 2013. Retrieved January 15, 2013.
  21. ^ National Atlas. Average Annual Precipitation, 1961-1990. Archived September 28, 2006, at the Wayback Machine Retrieved on 2006-06-15.
  22. ^ | last = Longman | first = R.J. | last2 = Giambelluca | first2 = T.W. | title = Climatology of Haleakala | journal = Climatology of Haleakalā Technical Report No. 193. | volume = 1 | issue = 1 | pages = 105–106 | date = 2015
  23. ^ Hereford, Richard, et al., Precipitation History of the Mojave Desert Region, 1893–2001, US Geological Survey, Fact Sheet 117-03, URL accessed 13 June 2006.
  24. ^ "USGS TNM 2.0 Viewer". Retrieved April 24, 2016.
  25. ^ "CONTIGUOUS UNITED STATES Climate Summary".
  26. ^ NOVA, Tornado Heaven, Hunt for the Supertwister, URL accessed 15 June 2006.
  27. ^ Baird, Joel Banner (August 4, 2013). "Stream-gage insight at risk from budget cuts". The Burlington Free Press. Burlington, Vermont. pp. 3C.
  28. ^ O'Connor, Jim E. and John E. Costa, Large Floods in the United States: Where They Happen and Why, US Geological Survey Circular 1245, URL accessed 13 June 2006.
  29. ^ QuickStats: Number of Heat-Related Deaths,* by Sex — National Vital Statistics System, United States,† 1999–2010§. (2012-09-14). Retrieved on 2013-07-29.
  30. ^ Hypothermia-Related Deaths - United States, 2003-2004. Retrieved on 2013-07-29.

External links

Autumn in New England

Autumn in New England begins in Late September and ends in late December, it marks the transition from summer to winter and is known for its vibrant colors and picturesque beauty. The autumn color of the trees and flora in New England has been reported to be some of the most brilliant natural color in the United States, as such it is a popular tourist destination, attracting visitors from across North America and overseas. Travelers flock to Vermont, New Hampshire, Maine, and parts of Massachusetts to see the colors each fall, a practice known as leaf peeping. Hiking during Autumn has become popular, and several areas offer guided tours.The combination of natural rugged landscape and rural, small town villages have made several areas in New England iconic locations for fall color photography. The numerous barns, church buildings, farmhouses, and villages combined with the vibrant seasonal colors makes for iconic photographs.

Climate of Alaska

The climate of Alaska is determined by average temperatures and precipitation received statewide over many years. The extratropical storm track runs along the Aleutian Island chain, across the Alaska Peninsula, and along the coastal area of the Gulf of Alaska which exposes these parts of the state to a large majority of the storms crossing the North Pacific. The climate in Juneau and the southeast panhandle is a mid-latitude oceanic climate (similar to Scotland, or Haida Gwaii), (Köppen Cfb) in the southern sections and a subarctic oceanic climate (Köppen Cfc) in the northern parts. The climate in Southcentral Alaska is a subarctic climate (Köppen Dfc) due to its short, cool summers. The climate of the interior of Alaska is best described as extreme and is the best example of a true subarctic climate, as the highest and lowest recorded temperatures in Alaska have both occurred in the interior. The climate in the extreme north of Alaska is an Arctic climate (Köppen ET) with long, cold winters, and cool summers where snow is possible year-round.

Climate of California

The climate of California varies widely, from hot desert to polar, depending on latitude, elevation, and proximity to the coast. California's coastal regions, the Sierra Nevada foothills, and much of the Central Valley have a Mediterranean climate, with warmer, drier weather in summer and cooler, wetter weather in winter. The influence of the ocean generally moderates temperature extremes, creating warmer winters and substantially cooler summers in coastal areas.

Climate of Florida

The climate of the north and central parts of the US state of Florida is humid subtropical. Most of South Florida has a tropical climate. There is a defined rainy season from May through October, when air mass thundershowers that build in the heat of the day drop heavy but brief summer rainfall. Late summer and early fall bring decaying tropical lows (and occasionally landfalling tropical cyclones) that contribute to late summer and early fall rains.

In October the dry season sets in across much of Florida (starting early in the month in northern Florida and near the end of the month in deep southern Florida) and lasts until late April in most years. Fronts from mid-latitude storms north of Florida occasionally pass through northern and central parts of the state which bring light and brief winter rainfall. Mid and late winter can become severely dry in Florida. In some years the dry season becomes quite severe and water restrictions are imposed to conserve water. While most areas of Florida do not experience any type of frozen precipitation, northern Florida can see fleeting snow or sleet a few times each decade.

The Gulf Stream running through the Florida Straits and then north off the Florida East Coast keeps temperatures moderate a few miles inland from around Stuart on the east coast to Ft. Myers on the west side of the state year round, with few extremes in temperature. The tropical ocean current also provides warm sea surface temperatures, giving Florida beaches the warmest ocean surf waters on the United States mainland.

Climate of Georgia (U.S. state)

The climate of Georgia is a humid subtropical climate with most of the state having short, mild winters and long, hot summers. The Atlantic Ocean on the east coast of Georgia and the hill country in the north impact the state's climate. Also, the Chattahoochee River divides Georgia into separate climatic regions with the mountain region to the northwest being cooler than the rest of the state, the average temperatures for that region in January and July being 39 °F (4 °C) and 78 °F (26 °C) respectively. Winter in Georgia is characterized by mild temperatures and little snowfall around the state, with the potential for snow and ice increasing in the northern parts of the state. Summer daytime temperatures in Georgia often exceed 95 °F (35 °C). The state experiences widespread precipitation. Tornadoes and tropical cyclones are common.

Climate of Hawaii

The American state of Hawaii, which covers the Hawaiian Islands, is tropical but it experiences many different climates, depending on altitude and surrounding. The island of Hawaii for example hosts 4 (out of 5 in total) climate groups on a surface as small as 4,028 square miles (10,430 km2) according to the Köppen climate types: tropical, arid, temperate and polar. When counting also the Köppen sub-categories the island of Hawaii hosts 8 (out of 13 in total) climate zones. The islands receive most rainfall from the trade winds on their north and east flanks (the windward side) as a result of orographic precipitation. Coastal areas are drier, especially the south and west side or leeward sides.

The Hawaiian Islands receive most of their precipitation during the winter months (October to April). Drier conditions generally prevail from May to September, and while warmer temperatures increase the risk of tropical cyclones, Pacific hurricanes seldom impact Hawai'i.

Climate of Illinois

The Climate of Illinois describes the weather conditions, and extremes, noted within the state of Illinois, United States, over time.

Because of its nearly 400 miles (640 km) length and mid-continental placement, Illinois has a widely varying climate. Most of Illinois has a humid continental climate (Köppen climate classification Dfa) with hot, humid summers and cool to cold winters. The southernmost part of the state, from about Carbondale southward, and the eastern suburbs of St. Louis, has a humid subtropical climate (Köppen Cfa) with more moderate winters. Average yearly precipitation for Illinois varies from 48 inches or 1,220 mm at the southern tip to 35 inches or 890 mm in the northern portion of the state. Normal annual snowfall exceeds 38 inches or 0.97 m in Chicago, while the southern portion of the state normally receives less than 14 inches or 0.36 m. The highest temperature recorded in Illinois was 117 °F (47.2 °C), recorded on July 14, 1954, at East St. Louis, while the lowest temperature was −38 °F (−38.9 °C), recorded on January 31, 2019, at Mt Carroll, Illinois.

Illinois averages around 50 days of thunderstorm activity a year which put it somewhat above average for number of thunderstorm days for the United States. Illinois is vulnerable to tornadoes with an average of 54 occurring annually, which puts much of the state at around 9.7 tornadoes per 10,000 square miles (30,000 km2) annually. The deadliest tornado on record in the nation occurred largely in Illinois. The Tri-State Tornado of 1925 killed 695 people in three states; 613 of the victims lived in Illinois.

Climate of Minnesota

Minnesota has a continental climate, with hot summers and cold winters. Minnesota's location in the Upper Midwest allows it to experience some of the widest variety of weather in the United States, with each of the four seasons having its own distinct characteristics. The areas near Lake Superior in the Minnesota Arrowhead region experience weather unique from the rest of the state. The moderating effect of Lake Superior keeps the surrounding area relatively cooler in the summer and relatively warmer in the winter, giving that region a smaller yearly temperature range. On the Köppen climate classification, much of the southern third of Minnesota—roughly from the Twin Cities region southward—falls in the hot summer humid continental climate zone (Dfa), and the northern two-thirds of Minnesota falls in the warm summer great continental climate zone (Dfb).

Winter in Minnesota is characterized by cold (below freezing) temperatures. Snow is the main form of winter precipitation, but freezing rain, sleet, and occasionally rain are all possible during the winter months. Common storm systems include Alberta clippers or Panhandle hooks; some of which develop into blizzards. Annual snowfall extremes have ranged from over 170 inches (432 cm) in the rugged Superior Highlands of the North Shore to as little as 5 inches (13 cm) in southern Minnesota. Temperatures as low as −60 °F (−51 °C) have occurred during Minnesota winters. Spring is a time of major transition in Minnesota. Snowstorms are common early in the spring, but by late-spring as temperatures begin to moderate the state can experience tornado outbreaks, a risk which diminishes but does not cease through the summer and into the autumn.

In summer, heat and humidity predominate in the south, while warm and less humid conditions are generally present in the north. These humid conditions initiate thunderstorm activity 30–40 days per year. Summer high temperatures in Minnesota average in the mid-80s F (30 °C) in the south to the upper-70s F (25 °C) in the north, with temperatures as hot as 114 °F (46 °C) possible. The growing season in Minnesota varies from 90 days per year in the Iron Range to 160 days in southeast Minnesota. Tornadoes are possible in Minnesota from March through November, but the peak tornado month is June, followed by July, May, and August. The state averages 27 tornadoes per year. Minnesota is the driest state in the Midwest. Average annual precipitation across the state ranges from around 35 inches (890 mm) in the southeast to 20 inches (510 mm) in the northwest. Autumn weather in Minnesota is largely the reverse of spring weather. The jet stream—which tends to weaken in summer—begins to re-strengthen, leading to a quicker changing of weather patterns and an increased variability of temperatures. By late October and November these storm systems become strong enough to form major winter storms. Autumn and spring are the windiest times of the year in Minnesota.

Climate of North Carolina

North Carolina's climate varies from the Atlantic coast in the east to the Appalachian Mountain range in the west. The mountains often act as a "shield", blocking low temperatures and storms from the Midwest from entering the Piedmont of North Carolina. Most of the state has a humid subtropical climate (Köppen climate classification Cfa), except in the higher elevations of the Appalachians which have a subtropical highland climate (Köppen Cfb). The USDA hardiness zones for the state range from zone 5a (-20°F to -15°F) in the mountains to zone 8b (15°F to 20°F) along the coast. For most areas in the state, the temperatures in July during the daytime are approximately 90 °F (32 °C). In January the average temperatures range near 50 °F (10 °C). (However, a polar vortex or "cold blast" can significantly bring down average temperatures, seen in the winters of 2014 and 2015.)

Climate of North Dakota

North Dakota's climate is typical of a continental climate with cold winters and warm-hot summers. The state's location in the Upper Midwest allows it to experience some of the widest variety of weather in the United States, and each of the four seasons has its own distinct characteristics. The eastern half of the state has a humid continental climate (Köppen climate classification Dfb) with warm to hot, somewhat humid summers and cold, windy winters, while the western half has a semi-arid climate (Köppen climate classification BSk) with less precipitation and less humidity but similar temperature profiles. The areas east of the Missouri River get slightly colder winters, while those west of the stream get higher summer daytime temperatures. In general, the diurnal temperature difference is prone to be more significant in the west due to higher elevation and less humidity.

Climate of Oregon

According to the Köppen climate classification, most of Western Oregon has a temperate oceanic climate (or Do type), which features cool summers, and wet winters with frequent overcast and cloudy skies. Eastern Oregon falls into the cool arid (or BSk type), which features drier weather.

West of the Cascade Mountains, winters are chilly with frequent rain and snow. Temperatures can get very cold, but only occasionally, as the result of Arctic cold waves. The high desert region of the state is much drier, with less rain, more snow, colder winters, and hotter summers.

Climate of South Carolina

South Carolina has a humid subtropical climate, with hot summers and mild winters. On average, between 40 inches (1,000 mm) and 80 inches (2,000 mm) of precipitation falls annually across the state. Tropical cyclones, and afternoon thunderstorms due to hot and humid conditions, contribute to precipitation during the summer and sometimes fall months, while extratropical cyclones contribute to precipitation during the fall, winter, and spring months. Tornadoes happen mostly in the spring with a secondary peak in November. Hail and damaging winds often occur in summertime thunderstorms. Tornadoes are very uncommon in the summer unless a tropical disturbance were to spawn one.

Climate of Texas

Texas' weather varies widely, from arid in the west to humid in the east. The huge expanse of Texas encompasses several regions with distinctly different climates: Northern Plains, Trans-Pecos Region, Texas Hill Country, Piney Woods, and South Texas. Generally speaking, the part of Texas that lies to the east of Interstate 35 is subtropical, while the portion that lies to the west of Interstate 35 is arid desert.

Texas ranks first in tornado occurrence with an average of 139 per year. Tropical cyclones can affect the state, either from the Gulf of Mexico or from an overland trajectory originating in the eastern Pacific Ocean. Those originating from the Gulf of Mexico are more likely to strike the upper Texas coast than elsewhere. Significant floods have occurred across the state throughout history, both from tropical cyclones and from stalled weather fronts.

Climate of Virginia

The climate of Virginia, a state on the east coast of the United States, is considered mild compared to other areas of the United States. Most of Virginia east of the Blue Ridge Mountains, the southern part of the Shenandoah Valley, and the Roanoke Valley, has a humid subtropical climate (Köppen climate classification Cfa). In the mountainous areas west of the Blue Ridge, the climate becomes humid continental (Köppen Dfa) and

maritime temperate (Köppen Cfb). Severe weather, in the form of tornadoes, tropical cyclones, and winter storms, impacts the state on a regular basis. Central Virginia received significant snowfall of 20 inches in December 2009.

Geography of the United States Virgin Islands

Geography of the United States Virgin Islands

The United States Virgin Islands are a group of several dozen islands and cays located in the Caribbean, about 1,100 miles (1,770 km) southeast of Florida, 600 miles (966 km) north of Venezuela, 40 miles (64 km) east of Puerto Rico, and immediately west and south of the British Virgin Islands.

The U.S. Virgin Islands lie near the boundary of the North American Plate and the Caribbean Plate, roughly 100 miles (161 km) south of the Puerto Rico Trench and near the Anegada Passage, a key shipping lane. Together with the British Virgin Islands, Vieques, and Culebra, they make up the Virgin Islands archipelago.

The hilly, volcanic islands of Saint Thomas (31 square miles (80 km2)) and Saint John (20 square miles (52 km2)) border the North Atlantic Ocean to the north and the Caribbean Sea to the south. The larger island of Saint Croix (84 square miles (218 km2)) lies 40 miles (64 km) to the south across the Virgin Islands Trough and is entirely in the Caribbean Sea.

Charlotte Amalie, Saint Thomas is one of the best natural, deepwater harbors in the Caribbean. The Islands have many well-known beaches, including Magens Bay (Saint Thomas) and Trunk Bay (Saint John), and coral reefs, including the Virgin Islands Coral Reef National Monument and the Buck Island Reef National Monument. More than half of Saint John and nearly all of Hassel Island are owned by the U.S. National Park Service.

Crown Mountain, on Saint Thomas, is the highest point in the U.S. Virgin Islands. Sea level is the lowest.

List of Northeast Snowfall Impact Scale winter storms

The Northeast Snowfall Impact Scale (NESIS) is a scale used to categorize winter storms in the Northeast United States. The scale was developed by meteorologists Paul Kocin and Louis Uccellini, and ranks snowstorms from Category 1 ("notable") to Category 5 ("extreme"). Only two historical blizzards, the 1993 Storm of the Century and the North American blizzard of 1996 are rated in the 5 "extreme" category. The scale differs from the Saffir–Simpson Hurricane Scale and Fujita Scale, which are used to classify tropical cyclones and tornadoes, respectively, in that it takes into account the number of people affected by the storm. The scale, as devised, is intended chiefly to assess past storms rather than assist in forecasts.


The Snowbelt is the region near the Great Lakes in North America where heavy snowfall in the form of lake-effect snow is particularly common. Snowbelts are typically found downwind of the lakes, principally off the eastern and southern shores. Lake-effect snow occurs when cold air moves over warmer water, taking up moisture that later precipitates as snow when the air moves over land and cools. The lakes produce snowsqualls and persistently cloudy skies throughout the winter, as long as air temperatures are colder than water temperatures, or until a lake freezes over.

In the United States, snowbelts are located southeast of Lake Erie from Cleveland, Ohio, to Buffalo, New York, and south of Lake Ontario stretching roughly from Rochester, New York, to Utica, New York, and northward to Watertown, New York. Other snowbelts are located on the eastern shore of Lake Michigan from Gary, Indiana, northward through Western Michigan and Northern Michigan to the Straits of Mackinac, and on the eastern and southern shores of Lake Superior from northwest Wisconsin through the northern half of the Upper Peninsula of Michigan.

Portions of the snowbelt are located in Ontario, Canada, which includes the eastern shore of Lake Superior from Sault Ste. Marie northward to Wawa, as well as the eastern and southern shores of Lake Huron and Georgian Bay from Parry Sound to London. During the winter, north-westerly winds cause frequent road closures, with Highway 21 on the Lake Huron coast and Highway 26 south of Georgian Bay as far east as Barrie, Ontario, being strongly affected. The Niagara Peninsula and the north-eastern shores of Lake Ontario are especially hard-hit by heavy snowfall when south-western winds are predominant.

Lake Erie is the second smallest of the five Great Lakes and the most shallow. It can completely freeze over during winter. Once frozen, lake-effect snow over land to the east and south of Lake Erie is temporarily alleviated. This does not end the possibility of a damaging winter storm. The Great Lakes Blizzard of 1977 that struck metropolitan Buffalo was a direct result of powder snow blown by high winds off Lake Erie, which had frozen earlier than normal. There was, for the region, no significant snowfall during the duration of the blizzard.

Healthy skiing industries have been established in snowbelt regions located near major cities such as Buffalo and Toronto. The Erie/Ontario snowbelt, which extends to the northern slopes of the Allegheny Plateau, has lent the region its nickname: ski country. To the south of Georgian Bay, ski resorts are found on the Niagara Escarpment at Blue Mountain and on the Oro Moraine.

United States temperature extremes

For the United States, the extremes are 134 °F (56.7 °C) in Death Valley, California in 1913 and −79.8 °F (−62.1 °C) recorded in Prospect Creek, Alaska in 1971.

The largest recorded temperature change in one place over a 24-hour period occurred on January 15, 1972 in Loma, Montana, when the temperature rose from −54 to 49 °F (−47.8 to 9.4 °C).

The most dramatic temperature changes occur in North American climates susceptible to Chinook winds. For example, the largest 2-minute temperature change of 49 °F (27.2 °C) occurred in Spearfish, South Dakota, a rise from −4 to 45 °F (−20.0 to 7.2 °C).

Climate data for United States
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 98
Record low °F (°C) −80
Source #1:
Source #2: (February, June, July, August record lows)
Climate data for Contiguous US average[24]
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Daily mean °F (°C) 30.8
Average precipitation inches (mm) 2.20
Source: NOAA (US)[25]
Climate of the United States
Federal district
Insular areas
Sovereign states
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other territories

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