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Heat waves in India usually take place between March and July and abate once the monsoon rains arrive. But in recent years these hot spells have become more intense, more frequent and longer.
India is among the countries expected to be worst affected by the impacts of climate crisis, according to the Intergovernmental Panel on Climate Change (IPCC).
"The future of heat waves is looking worse even with significant mitigation of climate change, and much worse without mitigation," said Elfatih Eltahir, a professor of hydrology and climate at MIT.
When the heat rises
And forecasters believe it's only going to get worse.
"In a nutshell, future heatwaves are likely to engulf in the whole of India," said AK Sahai and Sushmita Joseph, of the Indian Institute of Tropical Meteorology, in Pune in an email.
Survivability
Under the more optimistic prediction, researchers found that no parts of South Asia would exceed the limits of survivability by the year 2100.
However, it was a different story under the hotter scenario, which assumes global emissions continue on their current path.
In that case, researchers found that the limits of survivability would be exceeded in a few locations in India's Chota Nagpur Plateau, in the northeast of the country, and Bangladesh.
And they would come close to being exceeded in most of South Asia, including the fertile Ganges River valley, India's northeast and eastern coast, northern Sri Lanka, and the Indus Valley of Pakistan.
Survivability was based on what is called "wet bulb temperature" -- a combined metric of humidity and the outside temperature.
When the wet bulb reaches 35°C it becomes impossible for humans to cool their bodies through sweating, hence it indicates the survival temperature for humans. A few hours of exposure to these wet bulb conditions leads to death, even for the fittest of humans.
The places in India where it could become more difficult to survive overlap with already highly vulnerable areas, said Eun Soon, assistant professor at Hong Kong University of Science and Technology, who also took part in the MIT study.
"If we continue to produce the greenhouse gases at the current pace, one of the most populous regions in the world will not avoid the high risk of the deadly heat wave, facing an upper limit on human heat tolerance," she said.
What is the government doing about it?
India is still in the initial stages of developing a robust nationwide Heat Action Plan.
The Indian Meteorological Department (IMD) is working with state health departments to create an early warning system that would notify millions of people by text message about ways to stay cool, when heat waves hit.
At the same time, India is seeking long-term solutions.
A signatory to the 2015 Paris Climate Agreement, the country has pledged to cuts its carbon emissions by 33% to 35% below 2005 levels by 2030.
Given the more frequent heat waves and dire future predictions, capping a rise in global temperatures could very well turn out to be India's most important challenge in decades ahead.
The survivability of more than a billion people is at stake.
Correction: This story has been updated to reflect the correct temperature in Fahrenheit.