History books should be re-written again as on May 21, 2011, Karachi experienced one of the hottest days in years when temperature soared to 46°C. Last time temperatures touched this much was May 22, 1981.
Arabian sea keeps Karachi cool and pleasant!
Mostly when ever a heat wave affects Pakistan, Karachi escapes the wrath of the heat wave as south-west winds (sea breeze) keeps the temperature between 34°C to 36°C. But if these SW winds are blocked or killed by some weather related system then temperatures easily reaches 40°C during summer season. Monsoon systems over Indian Gujarat and Rajasthan while entering Sindh to move to Karachi also give rise to temperatures in the city as winds change from SW to NE (north-east).
In winters, same phenomena occurs when winds generated by western disturbance, from Balochistan decrease the temperatures in the city that gives the city a cold flu.
The reason of such unusual rise in temperature this time
This time it was the western disturbance that caused the temperatures to rise to 46°C. The western disturbance brought moisture laden winds to Punjab, Khyber and adjoining parts of other provinces. But it brought dry and hot winds for coastal parts of the country due to prevailing severe heat wave. These winds carried dust from the desert regions of Balochistan province that increased the temperatures in Karachi as winds direction changed from south-west (SW) to north-west (NW) on May 20. The sky also changed its colour from blue to dusty grey and hazy conditions prevailed in the city. The humidity also dropped from 70% to just 12% on Saturday May 21.
The highest temperature for Karachi ever recorded since the independence of Pakistan in 1947, was recorded on May 22, 1981 that was also 46°C. So a new version of this temperature has been recorded today (May 21). But no record broken but we can say that it has been highlighted once again.
In fact the highest temperature ever recorded in the living history of Karachi was 48.8°C, almost 50°C. This temperature was recorded in British India’s Karachi on May 9, 1938.
Heat wave to leave Karachi – But slowly
From May 22, the present heat wave will start to dissipate over Karachi but temperatures will remain around 39°C to 40°C and dusty conditions will prevail in the city till May 23. After that? Well, pre-monsoon winds will enter Karachi via coastal Gujarat that will give some cloudy cover to Karachi and south-eastern Sindh. Drizzle to light rainfall could also occur from May 24 to May 26.
Remember to take precautions during such extreme heat waves!