India is grappling with a summer of escalating intensity, as record-breaking heatwaves and soaring humidity push the country's power demand to new highs and test the limits of human endurance. The phenomenon extends beyond scorching afternoons, with dangerously warm nights becoming increasingly common. Over the last decade, the number of hot-humid days in India has dramatically increased from 14,086 to 16,970, signaling a profound shift in climatic patterns.
Intensifying Heatwaves: A Confluence of Factors
The current extreme weather conditions are a result of several converging factors. Persistent hot north-westerly winds, originating from the desert regions of Rajasthan, Punjab, and Haryana, are sweeping across central India, contributing significantly to the heat. Concurrently, human-caused climate change is elevating baseline temperatures, meaning heatwaves now begin from an already hotter foundation and reach more extreme peaks.
According to the Indian Meteorological Department (IMD), an analysis from 1961 to 2020 revealed an increasing trend of 0.1 days per decade in heatwave frequency across the core heatwave zone (CHZ). Severe heatwaves have also seen a rise in frequency, total duration, and maximum length within this zone. Furthermore, India's average humidity rose from 67.1% (2015-2019) to 71.2% (2020-2024), exacerbating the discomfort and health risks associated with high temperatures. The World Meteorological Organization (WMO) reported that 2025 was among the three warmest years globally, with temperatures nearly 1.44°C above pre-industrial levels. India's annual mean land surface air temperature until November 2025 was +0.29°C above the 1991-2020 average, making it the seventh warmest year since 1901.
The Peril of Hotter Nights
One of the most alarming aspects of this crisis is the persistence of high minimum temperatures. Night-time temperatures frequently settle in the late 20s°C, with some areas reaching 30°C. When nights remain hot, people, crops, and critical infrastructure receive insufficient recovery time from the day's heat. This lack of respite makes the overall heat stress far more dangerous than daytime heat alone. Data indicates that the all-India average night-time temperature increased by approximately 0.21°C per decade between 2010 and 2024.
A study by CEEW highlighted that 35 out of 36 states and union territories in India are experiencing night-time warming. Sikkim shows the strongest recent warming signal, while West Bengal, Andhra Pradesh, Karnataka, Goa, Uttarakhand, and Bihar also exhibit significant increases in average daily minimum temperatures.
Urban Heat Islands: Cities as Heat Traps
Indian cities are increasingly acting as urban heat traps, absorbing solar radiation during the day and slowly releasing it throughout the night. This phenomenon, known as the Urban Heat Island (UHI) effect, leaves millions exposed to prolonged thermal stress. Dense built-up areas, extensive use of concrete and asphalt, limited tree cover, waste heat from human activities, and poor ventilation all contribute to making urban centers significantly hotter than surrounding rural areas, particularly after sunset.
Over the past few decades, rapid urbanization has led to notable changes in local atmospheric conditions, resulting in surface temperatures that can be 2-10°C higher in cities compared to adjacent rural areas. The severity of the UHI effect varies across India, with the northwest region generally experiencing higher temperatures.