A recent study by the Council on Energy, Environment and Water (CEEW) has found that 57% of India’s districts—home to over three-fourths of its population—are now at high to very high risk from extreme heat. The report, “How Extreme Heat is Impacting India: Assessing District-level Heat Risk”, issues a stark warning: heat stress is no longer a seasonal discomfort but an accelerating disaster.
Using a composite Heat Risk Index (HRI) developed for 734 districts, the CEEW study identifies Delhi, Andhra Pradesh, Goa, Kerala, Maharashtra, Gujarat, Rajasthan, Tamil Nadu, Karnataka, and Uttar Pradesh as the 10 most heat-risk-prone states and Union Territories. The report is based on 35 indicators including frequency of very hot days, warm nights, rising humidity, population exposure, urbanisation trends, and health vulnerabilities.
One of the study’s most alarming findings is the rapid increase in very warm nights—defined as nights where minimum temperatures exceed the 95th percentile of historical norms. Over the past decade (2012–2022), nearly 70% of districts saw at least five more such nights per summer compared to the 1982–2011 average. In contrast, only 28% of districts experienced similar increases in very hot days.
Cities are bearing the brunt. Mumbai saw 15 additional very warm nights, Bengaluru 11, Bhopal and Jaipur 7 each, Delhi 6, and Chennai 4. This trend is largely attributed to the urban heat island effect, where concrete-heavy infrastructure traps heat during the day and releases it at night.
“Very warm nights prevent the human body from recovering after intense daytime heat. This significantly increases the risk of heat strokes and exacerbates conditions like hypertension and diabetes,” said Dr Vishwas Chitale, Senior Programme Lead at CEEW and co-author of the report.
The report also highlights a growing secondary risk: increasing relative humidity. The agriculturally dense Indo-Gangetic Plain has witnessed up to a 10% rise in humidity over the past decade. Cities traditionally considered dry, such as Delhi, Chandigarh, Kanpur, and Varanasi, are now recording humidity levels that push the “felt” temperature several degrees above the actual reading.
“High humidity hampers the body’s natural cooling mechanism—sweating—and elevates health risks even during moderately hot days,” said Arunabha Ghosh, CEO of CEEW. “We’re entering an era of prolonged heat, rising humidity, and dangerously warm nights. The science is unequivocal—we must act now.”
The study points out that extreme heat does not affect all districts or communities equally. Rural districts in Maharashtra, Kerala, Uttar Pradesh, and Bihar—where large populations work outdoors in agriculture or construction—are among the most vulnerable. These areas face compounding risks from both heat exposure and socio-economic factors such as poor healthcare access and higher prevalence of chronic diseases.
The analysis also notes that dense and rapidly urbanising districts—especially those with expanding built-up areas like Pune, Gurugram, and Mysuru—are becoming heat hotspots.
According to Aakash Shrivastava from the Ministry of Health and Family Welfare, data on heat stroke cases remains sparse due to the absence of electronic systems capturing doctor-patient interactions. “Heat stroke is a diagnosis based on clinical judgement, with no specific lab markers. This makes data collection difficult,” he said. However, advances under the National Digital Health Mission and platforms like the International Health Information Platform are improving reporting and transmission. “Thresholds identified in cities like Ahmedabad now serve as early indicators for heat-related deaths,” he added.
The report says, “India could lose the equivalent of 35 million full-time jobs and see a 4.5% GDP reduction by 2030 due to heat-related productivity losses.” Despite growing risks, the report finds that 95% of existing Heat Action Plans (HAPs) do not include detailed heat vulnerability assessments. This makes it challenging for local authorities to prioritise actions or access funding.
“India has made important strides with HAPs, but now needs to integrate granular risk data,” Chitale added. “States like Maharashtra and Odisha are pioneering this approach, but others must follow.”
The Ministry of Home Affairs, in 2024, made heatwaves eligible for funding under the State Disaster Mitigation Fund, a critical policy shift. The CEEW report urges states where over 50% of districts fall in the high-risk category to formally notify heatwaves as state-specific disasters. This would unlock an additional 10% of funds from the State Disaster Response Fund.
The report also recommends scaling affordable, climate-smart solutions like cool roofs, net-zero cooling shelters, parametric heat insurance, and ward-level early warning systems. CEEW is already working to support the development of 50 such localised heat action plans, aiming to reach 300 by 2027.
Akhil Srivastava of the India Meteorological Department noted that while heatwaves are not new, anomalies have been increasing. “In 2010, we recorded 578 heatwave days; this dropped for a decade, then spiked again to 455 days in 2022 and 536 in 2024,” he said. He attributed some of the spikes to El Niño conditions. “But intensity matters more than count—2015 saw high deaths with only 161 heatwave days. Other aggravating factors often worsen the toll on the public.”
In Tamil Nadu, this urgency is being felt acutely. “Heat coupled with high humidity causes severe thermal discomfort,” said Sudha Ramen, member of the Tamil Nadu State Planning Commission. “The urban heat island effect is spreading. Forest fires are rising, energy demand is surging, and vulnerable populations are increasingly at risk. This calls for collective action and greater sensitisation on heat mitigation.”