Rise in Humidity and Hot Nights as India’s Heatwaves Becomes More Relentless: Report
Heat-trapping cities, rising humidity, dry soils, and climate change driven warming, multiple factors are now converging to make extreme heat deadlier and more widespread
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India’s heatwaves are becoming more intense, long-lasting, and difficult to escape as rising temperatures combined with higher humidity, warmer nights, and rapid urbanisation, according to a new analysis by Climate Trends.
India’s core heatwave zone (CHZ) including states such as Rajasthan, Delhi, Uttar Pradesh, Madhya Pradesh, Bihar, Odisha, Telangana, and parts of Maharashtra, have witnessed a statistically significant rise in heatwave frequency and duration.
Large parts of India are already reeling under severe summer conditions, with temperatures crossing 45˚C in several regions. Banda in Uttar Pradesh recorded a maximum temperature of 48˚C.
Heatwave Duration and Frequency on the Rise
According to the India Meteorological Department (IMD), heatwave frequency in the CHZ has risen by 0.1 days per decade between 1961 and 2020, while the total duration of heatwaves has increased by 0.44 days per decade. Severe heatwaves have also become more frequent and prolonged during the period.
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 central India.
“In the absence of any weather system over the Indian mainland, hot northwesterly winds from the desert of the adjoining Sindh region of Pakistan and Rajasthan are penetrating deep into the country. The uninterrupted flow of these winds for the last three to four days has been pushing the mercury, resulting in heatwave to severe heatwave conditions. When the days are hot and there are no pre-Monsoon activities in the evening, these high temperatures are also reflected in higher nighttime temperatures,” said Mahesh Palawat, Vice President- Meteorology and Climate Change, Skymet Weather.
Increase in Night-time Temperature
India’s average night-time temperature has risen by around 0.21°C per decade between 2010 and 2024, according to the IMD.
According to the CEEW dataset, 35 of 36 states and union territories show warming on this measure. Sikkim has the strongest recent nighttime warming signal. West Bengal, Andhra Pradesh, Karnataka, Goa, Uttarakhand, and Bihar also show relatively strong increases.
Minimum temperatures have also been settling above average, further contributing to heat stress. Most of the night temperatures have been settling in the late 20s, and some stations have also reached 30°C. According to the WHO Housing and Health Guidelines, indoor air temperatures should not consistently exceed 24°C to prevent heat-related health risks, cardiovascular strain, and autonomic disruption during sleep.
Humidity is Worsening the Heat Stress
Humidity is also intensifying the impact of heatwaves. India’s average relative humidity rose from 67.1% between 2015 and 2019 to 71.2% between 2020 and 2024. Furthermore the number of “compound hot-humid days” days when both heat and humidity remain high, increased from 14,086 to 16,970 over the same period.
Rise in humidity is making heat stress worse, even where mean temperatures have not risen dramatically. The most intense combined heat-stress patterns are concentrated in coastal, tropical, and some densely populated inland states.
States with the largest recent rise in humidity between 2015–2019 and 2020–2024 include, Delhi, Chandigarh, Haryana, Telangana, Uttar Pradesh, Maharashtra, Rajasthan.
Cities Are Turning into Heat Traps
Urban heat island effects as a rising contributor to heat stress. Indian cities, characterised by concrete surfaces, dense construction and low tree cover, are increasingly trapping heat during the day and slowly releasing it at night. Studies cited in the report revealed urban temperatures can be 2 to 10 degrees Celsius higher than their rural surroundings.
