How is Delhi escaping heat wave while the rest of the country is suffering?

Summer, it seems, has come a tad early in India. Several parts, especially those in east and northeast, are under the brutal spell of heat wave. Even down south in Kerala, schools have been shut till May 6.

But, amid all this, the national capital Delhi has emerged as some sort of oasis, with mercury staying well below 40 degree Celsius so far. While the days are warm and bearable, nights are pleasant.

But why has Delhi been spared?

The India Meteorological Department (IMD) has observed that the presence of strong winds and overcast skies caused by western disturbances during April has helped moderate the temperature.

“When there is clear sky, chances of heat wave occurrence increase. Since there were no clear skies in Northwest India this month and even last month, there was no rise in temperatures,” Naresh Kumar, a scientist at the IMD, said.

Kumar said that Delhiites will be spared for another few days.

“In the coming weeks, temperature will only go up to 40 degree Celsius,” Kumar added.

The IMD scientist said that the weatherman will keep tracking developments over Haryana and south Rajasthan for the next two weeks for a possible heat wave occurrence.

“But the probability (of a heat wave) is quite less,” he added.

On Thursday, the Met department’s director general Mrutyunjay Mohapatra had cautioned that around 8-11 heat wave days are likely over south Rajasthan, west Madhya Pradesh, Vidarbha, Marathwada and Gujarat region in May.

The caution came as intense heat swept through eastern and southern parts of the country. The heat wave even prompted the Kerala government to order closure of educational institutions till May 6. 

The IMD said that heat wave to severe heatwave conditions scorched parts of West Bengal, Bihar, Odisha, Tamil Nadu, Telangana, and coastal Andhra Pradesh. At least 17 places in these states recorded temperatures above the 44 degree Celsius mark.

Talking about the current extreme heat wave situation prevailing in the eastern and southern parts of the country, Kumar attributed active jet streams in these regions as the culprit for high temperatures.

“Heat wave have been prevailing in east India for the last 15 days. Reason being that the jet stream has been active in this region, and winds are strong at low levels. Due to this, a divergence was created leading to direct sun rays reaching the ground,” he explained.

However, Kumar said that the situation is going to improve.

“In three days, there is a possibility of thunderstorm activity in the Bay of Bengal. This would lead to drop in temperatures in the east India region,” he said.

IMD defines a heat wave day as one where the maximum temperature exceeds the normal by 4.5 degrees Celsius or more, with the maximum temperature reaching at least 40 degrees Celsius. A heatwave is categorised as “severe” when the maximum temperature surpasses the normal by 6.5 degrees Celsius or more.