Is India getting hotter? What IMD data and recent studies actually show

Many Indian cities are facing heatwaves or near-heatwave conditions this summer. With a delayed monsoon and a likely El Nino during the June-September monsoon, heat stress is expected to grow. But a careful reading of official data shows the picture is more nuanced than a single ranking or a single hot day suggests.

According to the India Meteorological Department (IMD) outlook for May 2026, daytime maximum temperatures across most of India were expected to be normal to below normal. Above-normal readings were limited to the southern peninsula and parts of the north-east and north-west. Above-normal heatwave days were forecast only for specific regions — the Himalayan foothills, east-coast states, Gujarat and Maharashtra — while all-India May rainfall was projected at over 110 per cent of the long-period average.

The clearer long-term signal comes from an IMD study of the Core Heatwave Zone (CHZ) covering 1961-2020. It found heatwave frequency rising by 0.1 days per decade and duration rising by 0.44 days per decade. Nights are warming faster than days, at about 0.21 degrees Celsius per decade. The CHZ covers Punjab, Himachal Pradesh, Uttarakhand, Delhi, Haryana, Rajasthan, Uttar Pradesh, Gujarat, Madhya Pradesh, Chhattisgarh, Bihar, Jharkhand, West Bengal, Odisha, Telangana and parts of Maharashtra and coastal Andhra Pradesh.

Recent viral rankings of the worlds hottest cities should be read with care. One such list, based on 24-hour averages for a single day (April 27, 2026), captured a snapshot rather than a trend. It drew only from cities the website itself monitors — mostly in north and central India — and ignored West Asia, Africa and Australia. Ranking by 24-hour average also favours cities with warm nights and underplays desert cities that cool sharply after dark, which is why Rajasthan, holder of Indias all-time temperature record, appeared lower than expected.

In April 2026, IMD attributed relatively mild daytime temperatures to an unusually active run of western disturbances bringing above-normal rainfall. However, night-time temperatures stayed high — about 2.2 degrees above normal in Delhi and 2.4 degrees above normal in Punjab. This points to the urban heat island effect: concrete and asphalt store heat during the day and release it slowly at night, while reduced greenery and waste heat from air-conditioners make Indian cities 2 to 10 degrees hotter than surrounding rural areas.

A 2024 Nature Cities study found Indian cities warming at about 0.53 degrees per decade, against 0.26 degrees per decade for the country as a whole. But only about 38 per cent of the urban warming was due to urbanisation itself. Most of it was driven by background regional warming linked to climate change. An El Nino phase tends to weaken the monsoons moisture-bearing winds, lengthen dry break spells, and trigger humid heatwaves in the north-west.

For students, the takeaway is that India is warming overall, urban heat is a real phenomenon, but specific seasons and rankings need careful interpretation. The Core Heatwave Zone, the role of El Nino, urban heat islands and the long-term IMD trend are all high-yield exam concepts.