Heat Risk in India: Key Findings and Future Directions

Understanding Heat Risk and Its Distinction from Heatwaves

Heat risk pertains to the potential adverse effects on health or livelihoods resulting from elevated temperatures, even when official heatwave criteria are not met. It emphasizes the impact of heat on the human body, particularly due to sustained high nighttime temperatures and humidity, rather than merely focusing on extreme daytime heat.

Main Findings of the CEEW Study

The Council on Energy, Environment and Water (CEEW) study reveals several critical insights:

• 57% of Indian districts are categorized as facing high or very high heat risk.
• These districts encompass 76% of India's total population.
• States such as Delhi, Maharashtra, Tamil Nadu, Gujarat, Andhra Pradesh, and Uttar Pradesh are identified as facing the highest levels of risk.
• Urban regions with high population densities, including Mumbai and Delhi, are particularly vulnerable.

Drivers of Heat Risk in India

The study identifies three primary factors contributing to heat risk:

• Warmer nights: The occurrence of very warm nights has surged significantly from 2012 to 2022.
• Rising humidity: In North India, increased relative humidity impairs the body's cooling mechanism through sweating.
• Urbanization: Built-up areas absorb heat during the day and release it at night, leading to elevated nighttime temperatures.

Health Risks Associated with Warmer Nights

Very warm nights, characterized by temperatures exceeding the local 95th percentile, do not allow the human body adequate time to recuperate from daytime heat. This increases stress on vital organs such as the heart, lungs, and kidneys, significantly raising the risk of heatstroke, especially among vulnerable groups like the elderly, children, and individuals with pre-existing health conditions.

The Impact of Increasing Humidity

Regions like the Indo-Gangetic plain have seen relative humidity levels rise from 30-40% to 40-50% between 2012 and 2022. Elevated humidity not only worsens the discomfort index but also hinders the body's ability to cool down through perspiration, resulting in a rise in heat-related health issues.

Risks in Tier II Cities and Rapid Urbanizing Areas

Cities such as Pune, Gurugram, and Thoothukudi have experienced rapid urban development. These locations tend to absorb more heat due to extensive construction and subsequently release it at night, thus raising local temperatures. Moreover, they frequently lack sufficient green spaces and heat-resilient infrastructure.

Health Consequences of Extreme Heat

The escalation of heat levels can lead to dehydration, heatstroke, cardiovascular stress, and exacerbate chronic conditions like diabetes and hypertension. For instance, India reported over 44,000 heatstroke cases in 2024 alone.

Effectiveness of Government Heat Action Plans

Most Heat Action Plans (HAPs) in India are criticized for their lack of clear long-term strategies, inadequate funding, and a focus on district-specific needs. A March 2024 analysis by Sustainable Futures Collaborative found that only 5 out of 37 HAPs examined had the necessary legal support, resources, and actionable implementation strategies.

The Path Forward

• Revise and legally endorse Heat Action Plans.
• Focus on urban districts with high-risk profiles.
• Integrate early warning systems, healthcare preparedness, and water accessibility.
• Prioritize the development of heat-resilient infrastructure and public awareness initiatives.