The story so far:

Several cities in India are sweltering under heatwaves or quasi-heatwave-like conditions. The delayed onset of the monsoon and near certainty of an El Niño during the monsoon months of June-September will add to heat-related distress.

Was May 2026 an unusually hot month in India?

Not by daytime temperatures, and not nationally. The India Meteorological Department (IMD)’s outlook for May 2026 expected maximum temperatures to run ‘normal’ to ‘below normal’ across much of the country, with above-normal readings limited to the southern peninsula and parts of the north-east and north-west. Normal in most cases refers to a 30-year average temperature at a specific station and varies significantly. Above-normal heatwave days were forecast only for specific regions — the Himalayan foothills, the east-coast States, Gujarat, and Maharashtra — while all-India rainfall for May was projected to exceed 110% of the long-period average. The clearer signal is the long-term one: an IMD study of the Core Heatwave Zone (CHZ) over 1961–2020 found heatwave frequency rising 0.1 days per decade and duration 0.44 days per decade, both statistically significant trends. The study also found that nights warmed faster than days, at roughly 0.21°C per decade. The CHZ includes Punjab, Himachal Pradesh, Uttarakhand, Delhi, Haryana, Rajasthan, Uttar Pradesh, Gujarat, Madhya Pradesh, Chhattisgarh, Bihar, Jharkhand, West Bengal, Odisha, and Telangana, plus the meteorological subdivisions of Marathwada, Vidarbha, and Madhya Maharashtra, and coastal Andhra Pradesh. Heatwaves are becoming more frequent and longer over the decades, but May 2026 itself was a wet, regionally uneven month rather than a record-setting one.

A widely shared list claimed all 50 of the world’s hottest cities were in India in April. How sound is that?

It should be read with caution. The ranking, compiled by an air-quality website, captured a single day — April 27, 2026 — and presented it as a climate signal. One day cannot establish a trend, as the article itself acknowledges. The list was drawn from the cities the website monitors, overwhelmingly in north and central India. The absence of cities from West Asia, Africa, or Australia reflects the composition of the dataset. Ranking by 24-hour average temperature also favours places with warm nights and penalises desert cities that cool sharply after dark, which is why Rajasthan, home to India’s all-time temperature record, appeared near the bottom. The figures also came from the website’s own index rather than primary IMD station data, with no published method for the averages.

Was April 2026 hotter than April 2025?

By daytime temperatures, April 2026 was generally cooler. IMD attributed the relatively mild March and April to an unusually active run of western disturbances that brought above-normal rainfall. A year earlier, IMD had forecast above-normal maximum temperatures across most of the country for April 2025. The moderation in 2026, however, was largely a daytime effect: night-time temperatures stayed elevated, running about 2.2°C above normal in Delhi and 2.4°C in Punjab. The national average also masked sharp local extremes.

How do urban heat islands work, and what role does air-conditioning play?

When a city replaces soil and vegetation with concrete and asphalt, those surfaces absorb heat during the day and release it slowly at night. Combined with reduced evaporative cooling, low surface reflectivity, poor ventilation, and waste heat, this can make Indian cities 2–10°C hotter than surrounding rural areas, with the gap largest at night. Air-conditioning compounds it: each unit cools an interior by expelling heat outdoors.

Are urban heat islands a bigger driver of heat than climate change?

The evidence suggests not, in most cities. A 2024 study in Nature Cities found Indian cities warming at about 0.53°C per decade, against 0.26°C per decade for the country as a whole. But it attributed only around 38% of that urban warming to urbanisation itself, an enhancement of roughly 60% on top of the regional, climate-driven warming. Urban and background warming were strongly correlated, indicating that regional climate change drives much of the urban signal.

How will the emerging El Niño affect temperatures and the monsoon?

It raises the risk of a hotter, drier season. El Niño tends to weaken the monsoon’s moisture-bearing uplift, which can lengthen dry “break” spells and trigger humid heatwaves across the north-west.