New Delhi: As India battles the intensifying effects of climate change, a groundbreaking study by the Council on Energy, Environment and Water (CEEW) reveals that 76% of the country’s population—residing in 57% of its 734 districts—faces high to very high risk from extreme heat. Published on May 20, 2025, the study, titled How Extreme Heat is Impacting India: Assessing District-level Heat Risk, identifies Delhi, Maharashtra, Goa, Kerala, Gujarat, Rajasthan, Tamil Nadu, Andhra Pradesh, Madhya Pradesh, and Uttar Pradesh as the regions most vulnerable to heat-related challenges. With 2024 recorded as the hottest year globally and in India, this comprehensive analysis underscores the urgent need for robust, long-term strategies to combat the growing threat of extreme heat and protect millions of lives.
Defining Heat Risk: A Multifaceted Threat
To understand the severity of India’s heat crisis, it’s critical to distinguish between heatwaves, heat stress, and heat risk. Heatwaves are prolonged periods of abnormally high temperatures, varying by region—plains, coasts, or hills. Heat stress occurs when the human body temperature exceeds 37°C, impairing its ability to dissipate heat, leading to discomfort, heat cramps, exhaustion, and, if temperatures surpass 40°C, potentially fatal heat strokes. Heat risk, however, is the probability of experiencing heat-related illnesses or death due to exposure to extreme temperatures. According to the CEEW study, heat risk is driven by three key factors:
- Intensity of Heat: High temperatures, compounded by humidity, amplify the body’s inability to cool down.
- Degree of Exposure: Influenced by population density and urban environments.
- Community Vulnerabilities: Socio-economic conditions, health issues, and demographics such as age or disability increase susceptibility.
The CEEW researchers—Shravan Prabhu, Keerthana Anthikat Suresh, Srishti Mandal, Divyanshu Sharma, and Vishwas Chitale—developed a Heat Risk Index (HRI) to assess heat risk across India’s 734 districts. The HRI incorporates 35 indicators, including the frequency of very hot days, population density, percentage of persons with disabilities, and changes in land use and land cover. By analyzing 40 years of climate data (1982–2022), satellite imagery, and socio-economic factors, the study provides a detailed picture of India’s heat risk landscape.
Alarming Trends: Rising Warm Nights and Humidity
The study’s findings highlight several alarming trends driving India’s heat risk crisis. Between 2012 and 2022, the frequency of very warm nights—defined as nights when minimum temperatures exceed the 95th percentile of historical norms—outpaced the increase in very hot days. Over 70% of districts experienced five or more additional very warm nights per summer (March to June) during this period. This is particularly concerning because elevated nighttime temperatures prevent the body from recovering from daytime heat, increasing the risk of heat strokes and exacerbating chronic conditions like diabetes and hypertension.
Major urban centers are bearing the brunt of this trend. Mumbai saw an additional 15 very warm nights per summer in the last decade, followed by Bengaluru (11), Bhopal and Jaipur (7 each), Delhi (6), and Chennai (4). The urban heat island effect, where concrete infrastructure absorbs and retains heat, amplifies nighttime temperatures in cities, making them significantly hotter than surrounding areas.
Another critical factor is the rise in relative humidity in North India, particularly in the Indo-Gangetic Plain. Between 1982–2011, summer humidity in this region ranged from 30–40%, but it increased to 40–50% from 2012–2022. High humidity exacerbates heat stress by limiting the body’s ability to cool itself through sweat, especially when temperatures exceed 37°C. Cities like Delhi, Chandigarh, Jaipur, and Lucknow have seen early morning humidity rise by 6–9%, making even the start of the day feel oppressively hot. This is particularly dangerous for outdoor workers, such as farmers, who face heightened risks of heat-related illnesses.
Urbanization and Population Density: Amplifying Exposure
High population density and rapid urbanization are significant contributors to heat risk. Districts like Mumbai and Delhi, with populations exceeding 10 lakh, face the highest exposure due to dense buildings and limited green spaces. Tier II and III cities, such as Pune, Thoothukudi, and Gurugram, have experienced hotter nights due to the rapid expansion of concrete infrastructure between 2005 and 2023. This infrastructure traps heat during the day and releases it at night, intensifying the urban heat island effect.
States like Andhra Pradesh, Maharashtra, Haryana, Punjab, Chhattisgarh, Bihar, and Uttar Pradesh are particularly vulnerable due to a combination of high temperatures and socio-economic challenges. These regions have a higher proportion of elderly populations and a greater prevalence of non-communicable diseases, both of which increase susceptibility to heat-related illnesses. In contrast, districts in Odisha, with more green cover and water bodies, demonstrate better resilience to heat stress.
Heat Risk in the Himalayas: A Surprising Concern
Even the traditionally cooler Himalayan regions are not immune. In Jammu and Kashmir and Ladakh, the number of very hot days and very warm nights increased by over 15 days and nights per summer. These regions, with lower heat thresholds than the plains or coasts, face severe risks to their fragile mountain ecosystems, which could disrupt biodiversity and local livelihoods.
2024: The Hottest Year on Record
The year 2024 was the warmest on record globally, with average annual mean temperatures exceeding pre-industrial levels (1850–1900) by more than 1.5°C. In India, temperatures were approximately 1.2°C higher than the 1901–1910 average. The country experienced its longest recorded heat wave since 2010, with the first heatwave of 2025 recorded on February 27–28, significantly earlier than the previous year’s onset on April 5. In 2024, India logged over 44,000 heat stroke cases and 159 heat-related deaths, though experts believe these figures are underreported.
The economic and social impacts of extreme heat are profound. Studies estimate that India could lose the equivalent of 35 million full-time jobs and face a 4.5% reduction in GDP by 2030 due to heat-related productivity losses. Low-income households, with limited access to water and cooling, are disproportionately affected, as are outdoor workers, pregnant women, the elderly, children, and individuals with chronic health conditions. The World Health Organization reports that over 166,000 people died globally from heatwaves between 1998 and 2017, highlighting the global scale of the crisis.
Shortcomings in Heat Action Plans
India’s Heat Action Plans (HAPs), designed as early warning systems and preparedness strategies for extreme heat events, have significant gaps. A March 2025 study by the Sustainable Futures Collaborative (SFC) found that most HAPs lack long-term strategies to address the growing threat of extreme heat. Even cities with such strategies often fail to implement them effectively, leaving populations vulnerable to more frequent, intense, and prolonged heat waves. These deficiencies could lead to a surge in heat-related deaths in the coming years if not addressed.
Strategic Solutions for a Cooler Future
The CEEW study proposes four strategic solutions to bridge India’s heat resilience gap:
- Expand Heat Risk Planning: Incorporate warm nights, humidity, demographics, and health vulnerabilities into heat risk assessments, moving beyond a sole focus on daytime temperatures.
- Declare Heatwaves as State-Specific Disasters: States where over 50% of districts face high heat risk should classify heatwaves as disasters, unlocking targeted funding and resources.
- Create a National HAP Repository: A centralized repository would enhance transparency, facilitate cross-learning, and improve monitoring of Heat Action Plans nationwide.
- Leverage State Disaster Funds: In 2024, the Ministry of Home Affairs included heatwaves as a nationally eligible disaster for State Disaster Mitigation Fund (SDMF) project-based funding, which should be utilized to strengthen heat resilience.
A Call to Action
With 417 of India’s 734 districts classified as high or very high risk, and 76% of the population vulnerable to extreme heat, the CEEW study is a wake-up call for urgent action. States like Delhi, Maharashtra, and Gujarat face the highest risks, driven by rising nighttime temperatures, increasing humidity, and rapid urbanization. By addressing these challenges and prioritizing vulnerable communities, India can build a more resilient future. Policymakers, urban planners, and communities must collaborate to implement the study’s recommendations, ensuring that the nation is better equipped to handle the escalating heat crisis.
FAQs
1. What is heat risk, and how does it differ from heat waves and heat stress?
Heat risk is the probability of experiencing heat-related illnesses or death due to exposure to extreme temperatures, influenced by heat intensity (including humidity), exposure levels, and community vulnerabilities like age or health conditions. Heatwaves are prolonged periods of abnormally high temperatures specific to a region, while heat stress occurs when the body temperature exceeds 37°C, leading to discomfort, cramps, or heat strokes if it surpasses 40°C. The CEEW study emphasizes that heat risk is a broader concept, incorporating factors beyond just temperature spikes.
2. Which regions in India face the highest heat risk according to the CEEW study?
The study identifies Delhi, Maharashtra, Goa, Kerala, Gujarat, Rajasthan, Tamil Nadu, Andhra Pradesh, Madhya Pradesh, and Uttar Pradesh as the regions with the highest heat risk. Approximately 57% of India’s 734 districts, home to 76% of the population, fall into the high to very high risk categories, with 151 districts at high risk and 266 at very high risk.
3. Why are very warm nights a growing concern in India?
Between 2012 and 2022, the frequency of very warm nights—when minimum temperatures exceed the 95th percentile of historical norms—increased faster than very hot days. Over 70% of districts saw five or more additional very warm nights per summer. This is alarming because high nighttime temperatures prevent the body from cooling down after daytime heat, raising the risk of heat strokes and worsening conditions like diabetes. Cities like Mumbai (15 additional warm nights) and Bengaluru (11) are particularly affected due to the urban heat island effect.
4. How does rising humidity in North India contribute to heat risk?
The CEEW study found that relative humidity in North India, especially in the Indo-Gangetic Plain, rose from 30–40% (1982–2011) to 40–50% (2012–2022). Higher humidity exacerbates heat stress by limiting the body’s ability to cool through sweat, particularly when temperatures exceed 37°C. Cities like Delhi and Lucknow have seen early morning humidity increase by 6–9%, making conditions more dangerous, especially for outdoor workers.
5. What solutions does the CEEW study propose to address India’s heat risk crisis?
The study recommends four strategies:
Use State Disaster Funds: Leverage 2024’s inclusion of heatwaves in the State Disaster Mitigation Fund to strengthen resilience. These measures aim to bridge gaps in current Heat Action Plans, which often lack long-term strategies.
Expand Heat Risk Planning: Include warm nights, humidity, demographics, and health vulnerabilities in risk assessments.
Declare Heatwaves as State-Specific Disasters: States with over 50% of districts at high risk should classify heatwaves as disasters to access targeted funding.
Create a National HAP Repository: A centralized system to improve transparency and monitoring of Heat Action Plans.
