In charts: Beyond heatwaves, how warmer nights are making summer unbearable

Mint

14-06-2025

India is once again grappling with dangerous heatwave conditions, particularly across its northern, north-western and central regions, after an early monsoon briefly brought relief. Temperatures are around or above 40 degrees Celsius in Rajasthan, Madhya Pradesh, Punjab, Delhi and Haryana, among other places.
Though India is no stranger to extreme heat, warmer nights – an insidious climate pattern – are making summers agonising.
A recent study by the Council on Energy, Environment and Water (CEEW), a policy think tank, found that not only is India experiencing warmer nights, but nighttime temperatures are rising faster than daytime heat, creating conditions that prevent the human body from recovering from daily heat stress.
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An analysis of CEEW data, shared exclusively with Mint, shows that over a third of Indian districts analysed had five or more additional 'very warm nights' during 2012-2022 compared to historical trends during 1982-2011. Around 10% of these districts saw an additional 10 days of very warm nights during the decade to 2022. CEEW defines 'very warm nights' as periods when both minimum and maximum temperatures exceeded what was normally observed 95% of the time during 1982-2011.
Moreover, 'very warm nights' outnumbered 'very hot days' in about 26 years of the 1982-2022 period, with the longest streak witnessed between 2005 and 2018. While there have been more 'very hot days' than 'very hot nights' since 2019, both their numbers are significantly higher now. Years that witnessed El Nino, a climatic phenomenon that causes less rainfall, saw a spike in the number of very hot days and very warm nights, but the impact was more pronounced for very warm nights.
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Region-wise, districts in eight states—Gujarat, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Rajasthan, Tamil Nadu and Telangana—experienced more than 10 additional very warm nights each summer in 2012 and 2022 relative to 1982-2011.
In February 2025 the India Meteorological Department (IMD) included 'night temperature above normal' in their daily releases for the first time, Down to Earth reported. The weather agency regularly includes updates on warm night conditions in their daily releases, underlining the severity of the problem.
The pattern of extreme heat during days—with little or no relief during nights—brings severe health risks. 'Warmer nights prevent the human body from cooling down after intense daytime heat. This significantly increases health risks such as heat strokes and worsens non-communicable diseases such as diabetes and hypertension," CEEW said in the report released last month.
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Warmer nights are being observed in countries such as the UK and the US as well. According to an article published in The Conversation, warm nights have doubled in 50 years in Oxford, UK. Similarly, an analysis of 247 major US cities by Climate Central found they are currently experiencing about 27 warmer-than-normal days compared to the 1970s.
These trends are in line with the risks of climate change being seen around the world, with temperatures rising each passing year and heat conditions lingering longer than before. With global temperatures expected to keep rising—after hitting a record 1.55°C above pre-industrial levels (1850-1900) in 2024—conditions are likely to worsen.