Pakistan recorded one of the highest temperatures in the world – 53.5 °C (128.3 °F) – on 26 May 2010, the hottest temperature ever recorded in Pakistan, but also the hottest reliably measured temperature ever recorded on the continent of Asia. As Pakistan is located on a great landmass north of the Tropic of Cancer (between latitudes 25° and 36° N), it has a continental type of climate characterized by extreme variations of temperature, both seasonally and daily. Very high altitudes modify the climate in the cold, snow-covered northern mountains; temperatures on the Balochistan Plateau are somewhat higher. Along the coastal strip, the climate is modified by sea breezes. In the rest of the country, temperatures reach great heights in the summer; the mean temperature during June is 38 °C (100 °F) in the plains, the highest temperatures can exceed 47 °C (117 °F). In the summer, hot winds called Loo blow across the plains during the day. Trees shed their leaves to avoid loss of moisture. The dry, hot weather is broken occasionally by dust storms and thunderstorms that temporarily lower the temperature. Evenings are cool; the diurnal variation in temperature may be as much as 11C to 17C. Winters are cold, with minimum mean temperatures in Punjab of about 4 °C (39 °F) in January, and sub-zero temperatures in the far north and Balochistan.
The monsoon and the Western Disturbance are the two main factors which alter the weather over Pakistan; otherwise, Continental air prevails for rest of the year. Following are the main factors that influence the weather over Pakistan.
Pakistan has four seasons: a cool, dry winter from December through February; a hot, dry spring from March through May; the summer rainy season, or southwest monsoon period, from June through September; and the retreating monsoon period of October and November. The onset and duration of these seasons vary somewhat according to location.
The climate in the capital city of Islamabad varies from an average daily low of 2 °C in January to an average daily high of 38 °C in June. Half of the annual rainfall occurs in July and August, averaging about 255 millimeters in each of those two months. The remainder of the year has significantly less rain, amounting to about fifty millimeters per month. Hailstorms are common in the spring.
Pakistan's largest city, Karachi, which is also the country's industrial center, is more humid than Islamabad but gets less rain. Only July and August average more than twenty-five millimeters of rain in the Karachi area; the remaining months are exceedingly dry. The temperature is also more uniform in Karachi than in Islamabad, ranging from an average daily low of 13 °C during winter evenings to an average daily high of 34 °C on summer days. Although the summer temperatures do not get as high as those in Punjab, the high humidity causes the residents a great deal of discomfort. In Islamabad, there are cold winds from the north of Pakistan.
The weather extremes in Pakistan include high and low temperatures, heaviest rainfall and flooding. The highest temperature ever recorded in Pakistan is 53.5 °C (128.3 °F) which was recorded in Mohenjo-daro, Sindh on 26 May 2010. It was not only the hottest temperature ever recorded in Pakistan but also the hottest reliably measured temperature ever recorded on the continent of Asia. and the fourth highest temperature ever recorded on earth. The highest rainfall of 620 millimetres (24 in) was recorded in Islamabad during 24 hours on 24 July 2001. The record-breaking rain fell in just 10 hours. It was the heaviest rainfall in Islamabad in the previous 100 years.
Each year before the onset of monsoon that is 15 April to 15 July and also after its withdrawal that is 15 September to 15 December, there is always a distinct possibility of the cyclonic storm to develop in the north Arabian Sea. Cyclones form in the Arabian sea often results in strong winds and heavy rainfall in Pakistan's coastal areas. However tornadoes mostly occur during spring season that is March and April usually when a Western Disturbance starts effecting the northern parts of the country. It is also speculated that cycles of tornado years may be correlated to the periods of reduced tropical cyclone activity.
The drought has become a frequent phenomenon in the country. Already, the massive droughts of 1998-2002 has stretched the coping abilities of the existing systems to the limit and it has barely been able to check the situation from becoming a catastrophe. The drought of 1998-2002 is considered the worst drought in 50 years. According to the Economic Survey of Pakistan, the drought was one of the most significant factors responsible for the less than anticipated growth performance. The survey terms it as the worst drought in the history of the country. According to the government, 40 percent of the country's water needs went unmet.
Pakistan has seen many floods, the worst and most destructive is the recent 2010 Pakistan floods, other floods which caused destruction in the history of Pakistan, include the flood of 1950, which killed 2910 people; on 1 July 1977 heavy rains and flooding in Karachi, killed 248 people, according to Pakistan meteorological department 207 millimetres (8.1 in) of rain fell in 24 hours. In 1992 flooding during Monsoon season killed 1,834 people across the country, in 1993 flooding during Monsoon rains killed 3,084 people, in 2003 Sindh province was badly affected due to monsoon rains causing damages in billions, killed 178 people, while in 2007 Cyclone Yemyin submerged lower part of Balochistan Province in sea water killing 380 people. Before that it killed 213 people in Karachi on its way to Balochistan.
2010 July floods swept 20% of Pakistan's land, the flood is the result of unprecedented Monsoon rains which lasted from 28 July to 31 July 2010. Khyber Pakhtunkhwa and North eastern Punjab were badly affected during the monsoon rains when dams, rivers and lakes overflowed. By mid-August, according to the governmental Federal Flood Commission (FFC), the floods had caused the deaths of at least 1,540 people, while 2,088 people had received injuries, 557,226 houses had been destroyed, and over 6 million people had been displaced. One month later, the data had been updated to reveal 1,781 deaths, 2,966 people with injuries, and more than 1.89 million homes destroyed. The flood affected more than 20 million people exceeding the combined total of individuals affected by the 2004 Indian Ocean tsunami, the 2005 Kashmir earthquake and the 2010 Haiti earthquake. The flood is considered as worst in Pakistan's history affecting people of all four provinces and Gilgit–Baltistan and Azad Kashmir region of Pakistan.
The 2011 Sindh floods began during the monsoon season in mid-August 2011, resulting from heavy monsoon rains in Sindh, Eastern Balochistan, and Southern Punjab. The floods have caused considerable damage; an estimated 270 civilians have been killed, with 5.3 million people and 1.2 million homes affected. Sindh is a fertile region and often called the "breadbasket" of the country; the damage and toll of the floods on the local agrarian economy is said to be extensive. At least 1.7 million acres of arable land has been inundated as a result of the flooding. The flooding has been described as the worst since the 2010 Pakistan floods, which devastated the entire country. Unprecedented torrential monsoon rains caused severe flooding in 16 districts of Sindh province.