How Can We Keep Cool?

India is simmering with urban sprawl stoking sweltering days and scorching nights for three-quarters of its people.

India is heating up like never before. A whopping 57 percent of Indian districts, home to three-fourths of the population, now face very high heat risk with Maharashtra being one of the worst-afflicted states, as per a new study. Unmindful urbanization appears to be the real culprit and citizen will have to shed their cool to counter this heat menace.

Though the rains have brought down the ever-rising mercury under control since past few days, Maharashtra witnessed one of the worst heat wave days this summer. Still worse is the fact that in the coming days the intensity and the number of such heat wave days is likely to increase. A new study conducted by the Council on Energy, Environment and Water (CEEW) has shown that the extreme heat now poses a risk to 57 per cent of Indian districts that are home to 76 per cent of the population. Delhi, Andhra Pradesh, Goa, Kerala, Maharashtra, Gujarat, Rajasthan, Karnataka, Tamil Nadu, and Uttar Pradesh are the top ten most heat-risk-prone states and UTs according to this study.

CEEW’s study, ‘How Extreme Heat is Impacting India,’ offers the first comprehensive heat risk assessment across 734 districts using 35 indicators, mapping how climate change has reshaped heat patterns from 1982 to 2022. It finds 417 districts at high or very high risk, 201 at moderate risk, and 116 relatively low-risk - though none are immune. Three trends stand out: a surge in very warm nights, rising humidity in North India - especially the Indo-Gangetic Plain -and growing heat exposure in dense, urban and economically-vital centres like Delhi, Mumbai and Hyderabad. Further, some rural districts in Maharashtra, Kerala, Uttar Pradesh, and Bihar - home to large numbers of agricultural outdoor workers - were also found to fall in the ‘high’ to ‘very high’ heat risk category.

According to the study, approximately 70 per cent of districts have seen more than five additional very warm nights per summer over the past decade (2012-2022) compared to the climatic baseline (1982-2011). Very warm nights are defined as nights when the temperature stays unusually high - warmer than what used to be normal 95 per cent of the time in the past. By contrast, only about 28 per cent of districts saw a similar increase on very hot days. These warm nights are rising faster than hot days and make it harder for the human body to cool down and recover from daytime heat.

In the last decade, residents in Mumbai experienced 15 more very warm nights each summer compared to the previous three decades, while Jaipur and Chennai saw increases of seven and four nights, respectively. Urban heat islands, which trap heat by day and release it at night, are likely drivers of this trend, worsening health risks - especially for the elderly, outdoor workers, children, and those with conditions like hypertension and diabetes in both urban and rural areas.

The CEEW study also finds that relative humidity has increased by up to 10 per cent across the Indo-Gangetic Plain over the last decade. While coastal areas typically record 60–70 per cent relative humidity, North India historically experienced levels around 30–40 per cent. Over the past decade, this has increased to 40–50 per cent. Traditionally dry cities like Delhi, Chandigarh, Kanpur, Jaipur and Varanasi are now seeing higher humidity levels. Humidity can increase the ‘felt’ temperature by 3–5°C, making even moderate heat perilous. Once body temperature exceeds 37°C, sweating becomes essential for cooling, but high humidity hampers evaporation.

Amid rising heat-induced risks across the country, the report has recommended that Heat Action Plans (HAP) be regularly updated using granular data and expanded to include measures of night-time heat and humidity stress.

According to Dr. Vishwas Chitale, Senior Programme Lead at CEEW, India has made important strides in responding to extreme heat, but now must invest in long-term resilience. Solutions like parametric heat insurance, early warning systems, net-zero cooling shelters, and cool roofs must become core to heat action plans. States like Maharashtra, Odisha, Gujarat, and Tamil Nadu are leading by linking climate and health data in local planning. The next step is scaling such efforts nationally, guided by district-level risk assessments.

The study unequivocally states that we are entering an era of intense, prolonged heat, rising humidity and dangerously warm nights. Hence, this is the time when the citizens should come forth to push the administration to urgently overhaul city-level Heat Action Plans to address local vulnerabilities, balance emergency response measures with long-term resilience, and secure financing for sustainable cooling solutions. Further, it’s time to move beyond daytime temperature thresholds and act on what the data tells us: the danger doesn’t end when the sun sets.