Heatwave intensity, frequency and hotspot spread surge across India over 26 years: Study

Heatwaves in India have grown significantly more intense and frequent over the past 26 years due to global warming, according to a study published in Scientific Reports.

Beyond confirming existing trends, the research highlights a sharp expansion in heatwave-prone areas, with the extent of hotspots increasing by nearly 1.5 times. Regions most vulnerable to health impacts include western India, the southeastern coast, and the Indo-Gangetic Plain.

Rising heat, longer extremes

The India Meteorological Department defines a heatwave as a period when temperatures exceed 45°C or rise significantly above normal levels. A severe heatwave occurs when temperatures cross 47°C or surge even further beyond average conditions.

An analysis by scientists from the Indian Institute of Tropical Meteorology and the National Remote Sensing Centre shows that average daily maximum temperatures during April and May have steadily increased — by about 0.5°C by 2000 and 1°C by 2020 compared to 1981 levels. Northwestern and central India, along with coastal Andhra Pradesh, have seen the sharpest rise, while southern regions are also witnessing consistent warming.

The frequency of heatwaves has climbed markedly. Between 1981 and 2000, affected regions saw around 2.5 to 5.5 heatwave days annually. This rose to 3.5 to 8.5 days per year between 2001 and 2020. Not only are heatwaves more frequent, but they are also lasting longer, extending from roughly 2.5–4 days earlier to 3–5 days in many regions now.

Expanding hotspots and climate drivers

The study links these trends primarily to global warming, with additional influence from the El Niño–Southern Oscillation, which can intensify heat conditions during El Niño years. Researchers warn that continued warming will likely drive even more extreme and prolonged heatwaves.

Using satellite-based analysis, the study found that heatwave hotspots expanded dramatically — from about 1.19 million sq km (1981–2000) to 1.81 million sq km (2001–2020). These hotspots now cover large parts of northwestern, central, eastern, and peninsular India, indicating growing exposure to extreme heat.

Rising risk of heat-related deaths

The health implications are equally concerning. A report by the Climate Impact Lab warns that rising temperatures could significantly increase heat-related deaths, especially in low- and middle-income countries.

While India’s national average increase in mortality is projected at around 2.4 deaths per 1 lakh people, certain regions face far higher risks. Northwestern and north-central India could see 23–25 additional deaths per 1 lakh due to extreme heat — levels comparable to mortality rates from major diseases like tuberculosis and diabetes.

Globally, the burden is expected to be uneven, with over 90% of heat-related deaths occurring in lower-income regions. Within India, the hottest areas — already under stress — are likely to face the greatest impact.

A growing climate challenge

The findings underline a clear trend: heatwaves in India are no longer isolated weather events but part of a broader, intensifying climate pattern. With rising temperatures, expanding hotspots, and increasing health risks, the challenge now lies in adapting to and mitigating the impacts of extreme heat in the years ahead.