Extreme heat is impacting India, and how
As many as 57 per cent of Indian districts, home to 76 per cent of the population, are at risk from extreme heat, finds a new study launched by Council on Energy, Environment and Water (CEEW), New Delhi. The top 10 most heat-risk-prone states and UTs are Delhi, Andhra Pradesh, Goa, Kerala, Maharashtra, Gujarat, Rajasthan, Karnataka, Tamil Nadu, and Uttar Pradesh, it says.
The study also found that relative humidity has increased by up to 10 per cent across the Indo-Gangetic Plains over the past decade. While coastal areas typically record 60-70 per cent relative humidity, North India historically experienced levels around 30-40 per cent. Over the past decade, this has increased to 40-50 per cent. Traditionally drier cities like Delhi, Chandigarh, Kanpur, Jaipur and Varanasi are now seeing higher humidity levels. Humidity significantly raises the ‘felt’ temperature, sometimes by 3-5°C more compared to the recorded air temperature, making even moderate heat more dangerous. When body temperature exceeds 37°C, sweating is the primary cooling mechanism, but high humidity hinders evaporation.
The study, “How Extreme Heat is Impacting India: Assessing District-level Heat Risk”, presented composite heat risk assessment of 734 districts in India using 35 indicators, offering a granular picture of how climate change has reshaped heat hazard trends from 1982 to 2022. Of these, 417 districts fell in the high and very high risk categories while 201 were classified as moderate risk. The remaining 116 low-risk districts are not immune, only relatively less exposed.
The study has highlighted three key trends: an alarming rise in very warm nights; increasing relative humidity across North India, particularly in the Indo-Gangetic Plains; and heightened heat exposure in dense, urban, and economically critical districts such as Delhi, Mumbai, Ahmedabad, Hyderabad, Bhopal, and Bhubaneswar.
“Heat stress is no longer a future threat. It is a present reality. Increasingly erratic weather due to climate change — record heat in some regions, unexpected rain in others — is disrupting how we understand summer in India. We are entering an era of intense, prolonged heat, rising humidity, and dangerously warm nights. We must urgently overhaul city-level Heat Action Plans to address local vulnerabilities, balance emergency response measures with long-term resilience, and secure financing for sustainable cooling solutions. Further, it’s time to move beyond daytime temperature thresholds and act on what the data tells us: the danger doesn’t end when the sun sets,” says Dr Arunabha Ghosh, CEO of CEEW.
Very warm nights are defined as nights when the temperature stays unusually high — warmer than what used to be normal 95 per cent of the time in the past. These warmer nights are rising faster than hot days and make it harder for the human body to cool down and recover from daytime heat. In the last decade, residents in Mumbai experienced 15 more very warm nights each summer compared to the previous three decades, while Jaipur and Chennai saw increases of seven and four nights, respectively. Urban heat islands that trap heat during the day and release it at night are likely driving this trend. This has serious health implications, especially for the elderly, outdoor workers, children, and people with pre-existing conditions such as hypertension and diabetes, in both urban and rural areas.
Advocating investing in long-term resilience for India, Dr Vishwas Chitale, Senior Programme Lead, says, “Solutions like parametric heat insurance, early warning systems, net-zero cooling shelters, and cool roofs must become core to heat action plans. Now is the time to scale these efforts nationally, using district-level risk assessments to prioritise funding and action.”
The study recommends that heat-action plans (HAP) be regularly updated using granular data and expanded to include measures for night-time heat and humidity stress. These findings come at a critical time, as states now have access to the State Disaster Mitigation Fund, which in 2024 included heatwaves as an eligible disaster category. This enables state governments to mobilise dedicated funding for proactive and long-term heat resilience planning based on risk profiles.
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