Minimum temperatures are rising faster than maximum

Several parts of the country experienced many days of maximum heat, breaching 40 degrees Celsius last month. While this in itself is enough to make one sweat, literally and figuratively, a deeper look at last month’s weather pattern tells an interesting story — while maximum temperatures are getting warmer across the country, minimum temperatures are heating up relatively faster in many places. Across large parts of central and western India, the daily maximum temperatures were close to or even below the normal expected temperatures of those areas.

The “normal” here refers to IMD’s long-term baseline, which is the average April temperatures recorded at each station between 1991 and 2020. This 30-year reference period is the standard currently used by both the IMD and the World Meteorological Organization (WMO). So, when a station shows below-normal temperatures, it means April 2026 was cooler than that location’s April average, even if absolute temperatures were still high.

The IMD’s Monthly Climate Summary for April 2026 found that across the country, maximum temperatures were near normal — just 0.11 degrees Celsius above the long-period average — while minimum temperatures averaged 0.5 degrees Celsius above normal. In other words, maximums barely deviated from what April typically experiences, while minimums were warmer than expected.

The minimum temperature at Delhi’s Safdarjung station averaged 2.2 degrees Celsius above its normal while maximum temperatures averaged 0.3 degrees Celsius under the average. While the beginning of the month was relatively cooler, in the second half, Delhi’s minimum temperature was more than 1.5 degrees Celsius higher than expected, leaving the city little time to recover from the heat. Punjab told the same story as Delhi but even more starkly. April maximums averaged a degree below the expected value of 34.8 degrees Celsius, while minimums were 2.4 degrees Celsius hotter than the State’s average of 18 degrees Celsius.

Several Maharashtra stations also recorded higher minimum temperatures throughout April. Nagpur’s minimum temperatures were 3.6 degrees Celsius above the average of 23.9 degrees Celsius while its maximums at an average of 40.1, were just slightly above the normal of 40.6 degrees Celsius.

Maps 1 and 2 show how the variation in maximum temperatures was lower than the variation in minimum temperatures in April. Of the 442 stations for which data was available, Chaparmukh in Assam and Phulbani in Odisha deviated the most from their normal minimum temperatures, running 5.5 degrees Celsius and 5.1 degrees Celsius above their April baselines of 14.9 degrees Celsius and 19.6 degrees Celsius respectively.

The chart below shows four stations which had among the highest deviation in maximum and minimum temperatures from their normal values. A cooler night gives the body time to recover from the day’s heat. When that window closes, heat stress compounds across the day. The same logic applies to crops too. The UN Food and Agriculture Organization and WMO warned in an April report that high night-time temperatures force plants to keep burning the energy they built through photosynthesis in the day. This could cause stunted growth in plants.

Tehri in Uttarakhand and Thoothukudi in Tamil Nadu departed the most from their expected maximums. Andhra Pradesh, Maharashtra and Telangana were the States with the most number of days where the maximum temperature crossed 40 degrees Celsius.