These findings are drawn from a nationally representative survey of adults (18+) in India conducted by the Yale Program on Climate Change Communication and CVoter, an international survey company headquartered in Delhi, India.

Interestingly, in another report released last year, the Yale Program had found that a significant proportion (32%) of people in India had never heard of global warming. It highlighted the critical need to raise public awareness about climate change and local climate impacts, and reinforce the urgency of both reducing carbon pollution and preparing for future extreme events.

Warmer Nights a Growing Concern 

The CEEW team used high-resolution Indian Monsoon Data Assimilation and Analysis (IMDAA) climate data (12 km), satellite imagery, and the latest socio-economic and health datasets (National Family Health Survey 2019–21, Census 2011), to identify areas most at risk from the growing ‘invisible disaster’ of heat stress. IMDAA is the highest resolution reanalysis (12 km), currently available over the Indian monsoon region.

The analysis infers that over the last 40 years (1981–2022), heat extremes in India have increased linearly, contributing to major heatwaves in 2013, 2016, 2019, 2022, and 2024. However, in the last decade, very warm nights have increased faster than very hot days.

Nearly 70 per cent of districts experienced five or more additional very warm nights per summer (March to June), while only around 28 per cent of districts saw a similar increase in very hot days, states the report.

Warmer nights are particularly concerning as they make it harder for the body to cool down and recover from daytime heat.

According to the CEEW report, the rise in very warm nights is most evident in densely populated districts—often home to Tier I and II cities. For example, over the last decade, compared to the previous three, Mumbai experienced 15 more very warm nights per summer, Bengaluru 11, Bhopal and Jaipur 7 each, Delhi 6, and Chennai 4. This trend is likely largely driven by the urban heat island effect, where heat absorbed during the day is released at night, keeping cities warmer.

Districts with high human population density—including Mumbai, Delhi, and many parts of the Indo-Gangetic Plain—face the highest exposure to extreme heat, says the new report. Between 2005 and 2023, built-up areas have expanded rapidly, particularly in Tier II and III cities such as Pune, Thoothukudi, Kolhapur, Mysuru, Kozhikode, Ajmer, Gurugram, and Guwahati. Built-up and concretised surfaces trap heat during the day and release it at night, worsening nighttime heat.

The CEEW report also factors in relative humidity, which contributes to high heat stress. Relative humidity, a compounding factor of high heat, has increased by up to 10 per cent across North India and Indo-Gangetic Plain over the last decade, where farm workers spend long hours outdoors.

Traditionally drier cities such as Delhi, Chandigarh, Kanpur, Jaipur, and Varanasi are now seeing higher humidity levels, find the researchers. When body temperature exceeds 37°C, sweating is the primary cooling mechanism, but high humidity hinders evaporation causing heat stress.

According to CEEW, many districts in Andhra Pradesh, Maharashtra, Haryana, Punjab, Chhattisgarh, Bihar, and Uttar Pradesh are highly affected by extreme heat due to the combined impact of rising temperatures and underlying socio-economic and health vulnerabilities.

Extreme heat is having a multifaceted impact on day-to-day life. It is straining public health systems, pushing power demand to record highs, damaging crops, depleting water resources, and reducing the productivity of humans, livestock, and agriculture. Due to heat stress, India could lose the equivalent of 35 million full-time jobs and experience a 4.5 per cent reduction in GDP by 2030.

Recommendations by CEEW

The CEEW report stresses on the need to go beyond just daytime temperatures when planning for heat risk reduction. Most heat action plans (HAPs) still focus mainly on daytime temperatures. But extreme heat risks are also driven by warm nights, high humidity, and local vulnerabilities. To fill this gap, this study provides ready-to-use heat risk handbooks for every state and UT , with district-level maps and risk scores.

It recommends tapping into State Disaster Mitigation Funds to set up cooling shelters, early warning systems, and green infrastructure. It also says that states where more than half of districts face high heat risk should notify heatwaves as a state-specific disaster.

There is also a need to promote heat insurance to promote livelihoods. Parametric insurance—based on temperature thresholds—can enable quick payouts after extreme heat events, and should be scaled to protect outdoor workers and vulnerable communities.

The CEEW study also stresses on the need to create a national repository of HAPs. Lack of open access HAPs makes it hard to track what exists and what’s missing for institutional adaptive capacity. It recommends setting up an open-access national HAP repository, managed by the National Disaster Management Authority (NDMA), and updated by states, to support transparency, learning, and accountability.