From heat-trapping cities and rising humidity to dry soils and climate change-driven warming, multiple factors are now converging to make extreme more widespread than ever before.
As heatwaves sweep across India, the heat crisis is stretching beyond scorching afternoons into dangerously warm nights.
According to a study by the IMD, there is an increasing trend of 0.1 days/decade in the frequency of heat waves averaged over the core heatwave zone (CHZ) during 1961-2020. Severe heatwaves have also seen an increasing trend in the frequency, total number, and maximum duration in the CHZ.
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India’s average humidity increased from 67.1% to 71.2% between 2015-2019 and 2020-2024. Hot-humid days in India increased from 14,086 to 16,970 in the last decade.
According to meteorologists, the ongoing weather conditions are due to the unabated flow of hot north-westerly winds coming from the desert region across Rajasthan, Punjab, Haryana, till the central India.
Minimum temperatures have also been settling above average, further contributing to heat stress. Most of the night temperatures have been settling in the late 20°s, and some stations have also reached 30°C.
What is making heatwaves more intense?
From heat-trapping cities and rising humidity to dry soils and climate change-driven warming, multiple factors are now converging to make extreme more widespread than ever before.
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Human-caused climate change is increasing baseline temperatures, so heatwaves start from a hotter background and reach higher peaks. According to the World Meteorological Organization (WMO), 2025 was among the three warmest years ever recorded globally, with global temperatures reaching nearly 1.44°C above pre-industrial levels.
For India, the annual mean land surface air temperature for the country till November 2025 was +0.29°C above the 1991-2020 average and was the 7th warmest since 1901.
Hotter nights adding to distress?
When night-time temperatures stay high, people, crops, and infrastructure get less recovery time. This often makes heat stress much more dangerous than daytime heat alone.
The all-India average night-time temperature shows an estimated rise of about 0.21°C per decade over 2010-2024. While the warming is not perfectly smooth year to year due to interannual variability, the broader pattern still points upward, especially when comparing multi-year averages rather than single years.
About 35 of 36 states and union territories show warming on this measure, according to data by CEEW. Sikkim has the strongest recent night-time warming signal. West Bengal, Andhra Pradesh, Karnataka, Goa, Uttarakhand, and Bihar also show relatively strong increases. The value shown is the change in average daily minimum temperature between 2010-2014 vs 2020-2024.
What are Urban Heat Island effects?
Indian cities are increasingly functioning like heat traps, absorbing heat during the day and releasing it slowly at night, leaving millions exposed to prolonged thermal stress.
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Dense built-up areas, concrete, asphalt, low tree cover, waste heat, and poor ventilation can make cities significantly hotter than nearby rural areas, especially at night.
Over the last 3-4 decades, urbanisation in several parts of India has led to notable changes in the local atmosphere, accompanied by an increase in surface temperature relative to the adjoining rural regions. According to a study, the severity of the UHI varies from city to city in India, ranging from 2-10°C. The northwest region, in particular, tends to have higher temperatures.
Published on: May 22, 2026 6:07 PM IST
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