Subscribe
Heat waves, severe heat waves, hot and humid conditions and warm night conditions have started much earlier than normal across many states of India in 2025 and the reason is local weather phenomena being amplified by background global warming.
The Konkan region of Maharashtra and Goa were the first to record heat waves this year as early as February 25.
This is likely the earliest heat waves have ever been recorded in the country, though it is difficult to be sure as relevant data is not easily available from the India Meteorological Department (IMD). The month of February was the warmest on record for India, according to IMD.
Between February 25 and March 23, there were heat wave conditions declared on 12 days, according to data from IMD analysed by Down To Earth (DTE). Severe heat waves were experienced on eight days in the same period. Nine Indian states have suffered from either of the four heat-related events on at least on one day in the period.
Maharashtra suffered from heat waves on eight of the days while Gujarat experienced heat waves on six days and Odisha on four. Jharkhand experienced heat waves on two days while Goa, Karnataka, West Bengal, Chhattisgarh and Telangana did so on one day each.
Only two states — Gujarat and Odisha — on opposite sides of the country suffered from severe heat waves. Gujarat experienced the extreme conditions on five days and Odisha on four days.
The IMD considers declaration of a heat wave in a region when the maximum temperature crosses 40°C in the plains, 37°C in the coastal areas and 30°C in the hills. When this temperature is 4.5°C to 6.4°C above the normal for that particular day. IMD declares a severe heat wave when the anomaly is above 6.4°C.
Alternatively for the plains, the IMD also declares a heat wave when the absolute maximum temperature crosses 45°C and a severe heat wave when the temperature crosses 47°C on a particular day.
Since last year, the weather agency has also started declaring two new heat related events — hot and humid conditions and warm night conditions. IMD declares hot and humid conditions when the maximum temperature is 3°C above the normal in a place along with above normal relative humidity levels.
“A warm night is declared only when the maximum temperature remains 40°C or more. It is defined based on departures of actual minimum temperatures as follows: Warm night: minimum temperature departure is 4.5°C to 6.4°C. Very warm night: minimum temperature departure is >6.4°C,” writes IMD in its FAQ on heat waves. It does not mention coastal areas or hills separately in its definition for warm nights.
In the current season IMD has declared hot and humid conditions on four days between February 25 and March 2. The coastal Konkan region of Maharashtra suffered from hot and humid conditions on three of the days while Goa and Gujarat on two days each. The Konkan region also suffered from heat waves on two of the days and Goa on one day.
IMD has recorded warm night conditions this season only on March 15 in Odisha and Jharkhand. The reasons for these varied heat-related events are both regional and global.
“There has been an anticyclone at the upper level that covers all of the Indian Ocean and the subcontinent. It exists at the mid-level as well as at the surface, but it splits into two anticyclones — one over the Bay and the other over the Arabian Sea,” Raghu Murtugudde, professor of climate studies at the Indian Institute of Technology, Bombay and emeritus professor at the University of Maryland told DTE.
“The Arabian Sea anticyclone is pulling winds from the north-northwest into the coastal regions causing early heatwaves,” he added. Murtugudde contends that background warming may have had a role to play but the exact mechanisms need to be studied further.
“It is unclear if the upper-level anticyclone is related to global warming or just a freak weather phenomenon. But the lower-level heat sweeping into the coastal regions causing is definitely related to the heating over the Middle East, northern Arabian Sea and the northwestern regions of India. Once again, global drivers and local amplifiers,” explained Murtugudde.