Eastern heatwave part of broader Asian surge

There’s a line dividing India’s north and northwest from its east and the peninsula — and it has nothing to do with the ongoing elections.
North of the line, temperatures in the ongoing Indian summer are still moderate. Delhi, for instance, is still recording temperatures around or below the normal mark, with a maximum of 38.1°C on Friday.
But south of it, the story is different.
Heat wave to severe heat wave conditions have been prevailing over Odisha since April 15, Gangetic West Bengal since April 17, Jharkhand and sub-himalayan West Bengal, Rayalaseema since April 24 and Bihar since April 26, the India Meteorological Department said on Friday.
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And it emerges that this trend continues outside India, to countries south of this figurative line across South and Southeast Asia.
Bangladesh had to close down schools last week as maximum temperatures soared well above 40°C.
Myanmar’s Chauk recorded 48.2°C on April 28. The Philippines closed schools and warned of overloading on its power grid due to extreme heat this week.
In Thailand, temperatures crossed 40°C in 26 provinces in April, according to the Thai Meteorological Department. The northern province of Lampang has seen the highest temperature so far this year at 44.2°C this week.
“Huge number of heat records in Southeast Asia lately. VIETNAM tied its national April record with 44.0°C (Tương Dương). LAOS broke all-time national record with 43.6°C (Tha Ngon & Seno). PHILIPPINES Manila metro all-time record exceeded with 38.8°C,” Scott Duncan, a meteorologist, wrote on X on Thursday.
“The lingering heat from El Nino (that is now dissipating) riding on the background global warming during the peak of summer makes it hotter than usual,” said Roxy Mathew Koll, climate scientist at Indian Institute of Tropical Meteorology.
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Closer home, West Bengal’s Kalaikunda recorded 44.2°C on Thursday, 7.5 degree C above normal.
The heatwave conditions are likely to continue over East India till May 5, and over south Peninsular India till May 6, and abate thereafter, IMD has said.
Meanwhile, north of the line, things are different.
“India’s North is experiencing Western Disturbances that are bringing the temperatures down. Also, the heat is yet to progress north along with the seasonal cycle,” Koll added.
A western disturbance this weekend is forecast to bring a dust storm and light rain to Delhi-NCR on Saturday evening. Wind speed is expected to touch up to 45 km/hr in parts of the region, which should bring the maximum temperature down by 1-2°C, the IMD has said.
This year’s spring/early summer Asian heat wave is similar to March 2022 when the Indian subcontinent experienced a severe spring heat wave which is estimated to have led to at least 90 deaths across India and Pakistan, and triggered an extreme Glacial Lake Outburst Flood (GLOF) in northern Pakistan and forest fires in India. The heat reduced India’s wheat crop yields, causing the government to reverse an earlier plan to export the grain to supplement the global wheat supply that was impacted by the war in Ukraine.
Except, the heat stress in 2022 was mostly concentrated over Pakistan and northwest India.
Prolonged heatwaves affected South and South-East Asia in early summer last year also.
This year, despite normal to below normal temperatures over northwest India, extreme temperatures over rest of the country especially east and south peninsular India made this April among the warmest since 1901. The mean temperature for the country was 29.06°C, 0.76°C above normal.
It was the warmest April in eastern and northeastern India in terms of both mean and night temperatures since records began in 1901, according to updated analysis presented by IMD on Wednesday. The minimum temperature over the region in April was 1.78°C above normal and mean temperature was 2°C above normal.
For south peninsular India, it was the second-warmest April since 1901 with average maximum temperature recorded 1.35°C above normal; minimum temperature was 1.09°C above normal and mean temperature 1.22°C above normal, according to IMD. Rainfall during April 2024 over south peninsular India was 12.6mm — the fifth lowest since 1901.
IMD on Friday warned that there is likely to be a rise in maximum temperatures by 4-6°C over many parts of northwest India till early next week.
“This is due to a synoptic system that is prevailing over south peninsula. A large anticyclone (clock wise flow) at about 3km (height). This increases surface temperature. Lack of rains and low soil moisture during past few days also adds to this; the other factor is cloudless skies which allow solar radiation to penetrate more in to the surface. Due to anticyclone flow winds are from land to sea along the east coast which don’t allow cool sea breeze to set in. This episode was well predicted by the models,” M Rajeevan, former secretary, ministry of earth sciences and climate scientist, said on Tuesday.
In an April 22 interview Friederike Otto, Senior Lecturer in Climate Science at Grantham Institute – Climate Change and the Environment, Imperial College London warned that heat waves would get more intense in coming years.
“With millions of people living in poverty and extremely hot summers, heat is a massive challenge for India. Heatwaves are the deadliest type of extreme weather there is. They’re often referred to as ‘silent killers’. In April last year, an intense humid heatwave hit India. While the total number of deaths related to that heatwave is unknown, its likely hundreds or even thousands of people would have died. In Europe, which is less hot and has a less exposed population, 70,000 deaths were linked to high temperatures in a single year. In India, our study found that human-caused climate change made heatwave at least 30 times more likely and at least 2°C hotter. Similar heatwaves with temperatures well above 40°C will become hotter and hotter in India as the climate warms, so India needs to prepare,” she said.