India's nights are heating up faster than days, 76% population at risk

A new national study finds night-time temperatures rising faster than daytime highs in 70% of districts, exposing millions to prolonged, dangerous levels of heat stress

As India burns in record-breaking summers, a new report has revealed that 57 per cent of Indian districts—home to 76 per cent of the population—are now at high or very high risk from extreme heat. The study, conducted by the Council on Energy, Environment and Water (CEEW), spans four decades from 1982 to 2022 and maps heat risk across all 734 districts using 35 indicators of hazard, exposure, and vulnerability.

 

Unlike earlier assessments that focused only on daytime temperatures, CEEW’s report incorporates night-time heat and relative humidity, offering a clearer view of how climate change has intensified the duration and intensity of heat hazards.

 

 

Night-time temperatures rising faster than daytime heat

 

The study found that very warm nights are increasing more rapidly than very hot days. In the last decade alone, nearly 70 per cent of districts recorded at least five additional very warm nights per summer, while only 28 per cent showed a similar rise in daytime heat. This trend is more pronounced in urban areas due to the urban heat island effect, where concrete and built-up surfaces trap heat and release it slowly at night. 

   

Metro cities saw stark changes: Mumbai recorded 15 more warm nights per summer in the last decade; Bengaluru had 11, Bhopal and Jaipur 7, Delhi 6, and Chennai 4. Warm nights prevent the human body from recovering from daytime heat, increasing the risk of heatstroke and other health issues, especially among vulnerable groups.

 

Rising humidity worsens heat stress in the Indo-Gangetic Plain

 

Traditionally dry cities in the Indo-Gangetic Plain are now facing a sharp rise in humidity—up to 10 per cent higher over the past decade. Cities like Delhi, Chandigarh, Kanpur, Jaipur, and Varanasi are experiencing higher relative humidity levels, severely compromising the body’s ability to cool itself through sweating.

 

Farmers in high-humidity zones are at greater risk of heat stress, as high humidity significantly reduces sweat evaporation, crucial for thermoregulation when body temperatures exceed 37°C.

 

Which states and districts are most vulnerable?

 

The ten states and Union Territories with the highest cumulative heat risk are Delhi, Maharashtra, Goa, Kerala, Gujarat, Rajasthan, Tamil Nadu, Andhra Pradesh, Madhya Pradesh, and Uttar Pradesh.  Also read: Delhi weather: Why IMD keeps predicting rain but the heat won't quit

 

Many districts in Andhra Pradesh, Maharashtra, Haryana, Punjab, Chhattisgarh, Bihar, and Uttar Pradesh are flagged as high-risk due to a dangerous combination of rising temperatures and socio-economic vulnerabilities such as poor health infrastructure and lower income levels.

 

Urbanisation and concretisation driving local heat surges

 

Between 2005 and 2023, built-up areas have surged—especially in Tier II and III cities like Pune, Thoothukudi, Kolhapur, Mysuru, Kozhikode, Ajmer, Gurugram, and Guwahati. The rapid pace of concretisation contributes to higher heat absorption during the day and its slow release at night, aggravating night-time temperatures.

 

Districts with high population densities, like Mumbai and Delhi, are facing the worst exposure, making urban residents disproportionately vulnerable to prolonged heat.

 

States can now use disaster funds to mitigate heatwaves

 

In 2024, heatwaves were officially recognised as eligible for funding under the State Disaster Mitigation Fund (SDMF). This enables states to finance interventions such as cooling shelters, early warning systems, green infrastructure, and heat-resilient urban planning.

 

States where more than 50 per cent of districts face high heat risk can also notify heatwaves as a state-specific disaster, unlocking an additional 10 per cent of funds from the State Disaster Response Fund (SDRF). Maharashtra, Tamil Nadu, and Andhra Pradesh have already made this declaration.

 

Most Heat Action Plans miss key risks like humidity and night heat

 

Many first-generation Heat Action Plans (HAPs) across Indian states fail to account for night-time heat, humidity, and local vulnerabilities—focusing mainly on peak daytime temperatures.

 

CEEW urges local administrations to integrate India Meteorological Department (IMD) alerts—such as percentile-based temperature thresholds, warm night forecasts, and humid heat advisories—into local early warning systems and HAPs.

 

Heat insurance can offer pre-emptive protection

 

CEEW recommends expanding parametric heat insurance models, where payouts are triggered automatically when temperatures cross defined thresholds. Pilots in Nagaland and for SEWA workers in Ahmedabad can serve as templates to protect farmers, outdoor labourers, and low-income workers across India.

 

These models shift disaster response from post-event relief to pre-arranged financial protection, improving resilience against recurring heatwaves.

 

A national Heat Action Plan repository is urgently needed

 

Currently, no central repository exists to track the status, scope, or effectiveness of Heat Action Plans. The report proposes a national, open-access HAP repository managed by the National Disaster Management Authority (NDMA), with regular updates from states.

 

Such a repository could improve transparency, coordination, and policy accountability across India’s increasingly heat-vulnerable landscape.