Heat waves to last longer and affect larger regions across India, warn scientists

New Delhi: Heat waves in India are expected to last longer and affect larger regions, scientists have warned, as climate change continues to intensify extreme weather events.

Climate models show that the area and duration of heat waves in India would increase, said Krishna Achuta Rao, Head, Centre for Atmospheric Sciences at Delhi's Indian Institute of Technology (IIT).

Speaking at the India Heat Summit 2025, organised by research group Climate Trends, Rao said "this means the northern plains and several states across the southern peninsula will experience heat waves that last longer and cover larger areas".

"What might have been a week-long event could turn into a month-and-a-half or two-month-long event. Our future looks very stark," he added.

The scientist said the models also suggest that heat waves may occur during the monsoon months which could be more dangerous.

"This is especially worrying because it will be hot and humid, with temperatures above 40 degrees Celsius," added Rao.

The Intergovernmental Panel on Climate Change's (IPCC) sixth assessment report and recent scientific papers have warned of more frequent and intense heat waves in South Asia even during monsoon months.

Farooq Azam, senior cryosphere specialist at the International Centre for Integrated Mountain Development (ICIMOD), said the rising temperatures are melting glaciers faster, affecting water availability in India's rivers.

Azam said the country depends heavily on water from glaciers for agriculture and electricity generation.

At present, there is more water because of warming-driven glacier melt, but there is a threshold beyond which glaciers will start contributing less water, called peak water. Some models project that peak water could occur around 2050 in the Indus, Ganga and Brahmaputra river basins, while some studies suggest it may have already been reached in the Brahmaputra system, he added.

Azam warned that this could mean "more floods until 2050" and water shortages afterwards.

He said that 2022 saw the most negative glacier mass balance -- more ice was lost than gained -- although annual temperatures were higher in 2023 and 2024.

"This is because early heat waves in March 2022 led to early melting of glaciers, resulting in high river flows when water was not needed. The early heat waves and early monsoon contributed to the devastating floods in Pakistan that year," added Azam.

ICIMOD's Hindu Kush Himalaya Assessment and studies by the World Weather Attribution have linked glacier melt and climate change to increased flood risk in the region.

The senior cryosphere specialist also said that glacier melt in the Himalayas has more immediate impacts than glacier loss in Iceland or the Arctic, as the Himalayan glaciers supply water to more than a billion people in the Indus, Ganga and Brahmaputra river basins.