India’s dangerously torrid summer days have long been a climate warning. Now the country is increasingly dealing with sweltering nights too, as global warming and poor urban planning put millions at risk.
For eight of the past 10 years, average minimum temperatures during March to May — a proxy for nighttime heat over the pre-monsoon season — have been higher than the long-term average, according to data from the India Meteorological Department. Only 2020 and 2023 bucked the trend.
Earlier this month, the IMD warned this summer would again see above-normal minimum temperatures across India. That means heat will linger even when cooler weather should instead be allowing humans and power infrastructure to recover from the day’s strain, putting both at risk.
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“Sustained high temperatures through the night are becoming a bigger cause of heat exhaustion than the day-time heat,” said Rohit Magotra, a director at New Delhi-based think-tank Integrated Research and Action for Development, or IRADe, who advises the Indian government on heat mitigation. “Especially for people without access to adequate water and consistent, affordable cooling.”
Part of the problem is a changing climate — India is one of the most vulnerable nations when it comes to the effects of rising temperatures.
But hotter nights are also the consequence of so-called urban heat islands, when concrete in densely packed neighborhoods absorbs daytime solar radiation and slowly releases the trapped heat at nights, pushing the indoor temperatures above the outside readings. In the poorest areas of India’s cities, inhabitants often work outdoors by day — and now struggle to recuperate in the evening.
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“Climate change is driving baseline temperatures higher, but the way we build our cities is what traps that heat,” said Vishwas Chitale, team lead for climate resilience at the New Delhi-based Council on Energy, Environment and Water. “More than half of extreme heat in India cities is driven by rapid concretization and expanding road networks.”
