New Delhi
Clear skies and warm, dry northerly winds led to Delhi on Monday recording its first heatwave day of the summer season, as the maximum temperature crossed the 40-degree mark to settle at a high of 40.2 degrees Celsius (°C). This was the highest maximum so far this season, eclipsing the previous high of 39°C on April 3.
The India Meteorological Department (IMD) has issued a yellow alert for the National Capital Region, warning that heatwave conditions will continue across Delhi-NCR on both Tuesday and Wednesday. However, a western disturbance is likely to influence the region, and is predicted to bring relief from the heat from Thursday, IMD officials said.
The 40.2°C recorded on Monday was logged at the Safdarjung observatory — Delhi’s base weather station — which was five notches above the normal for this time of the year. Other parts of the city were even warmer: both the Ridge and Ayanagar stations were the joint-hottest locations in the city, with a maximum of 41°C. This was 6.1°C above normal at Ayanagar, and 5.9°C above normal at the Ridge station, data showed.
According to IMD, a heatwave is when the maximum temperature is above 40°C, while the departure from normal is 4.5°C or more. It is also a heatwave if the maximum is over 45°C in the plains. IMD calls it a “severe heatwave” when the maximum is above 40°C, and the departure is 6.5°C or more above normal.
“Three weather stations — Safdarjung, Ridge, and Ayanagar — satisfied the criteria for heatwave. Heatwave conditions are likely to continue till April 9,” said IMD scientist Krishna Mishra.
The last time Delhi had a heatwave in April was in 2022, when the city logged four consecutive such days between April 8 and 11.
The minimum temperature also increased substantially, climbing to 20.2°C on Monday. Though normal for this time of the year, the minimum was 18.5°C the previous day. IMD forecasts the minimum to be between 21-23°C on Tuesday and between 22-24°C on Wednesday.
Weather experts said NCR is likely to have some relief from the heat Thursday onwards, as a western disturbance begins to influence the region.
“It has crossed 40°C for the first time this season at Safdarjung and a further rise is expected on Tuesday and Wednesday. It may touch 42°C in parts of the city, before marginal relief is seen from Thursday onwards, as a western disturbance approaches, causing cloudiness. This will mean a dip of 2-3°C again in the region,” said Mahesh Palawat, vice president at Skymet meteorology.
IMD data shows generally, temperature crosses the 40°C threshold in the second half of April. Last year, this happened on April 26 (40.5°C). In 2023, it was on April 15 (40.5°C), and on April 7 (40°C) in 2022. The earliest it has happened in the last decade was March 30 in 2021, when the maximum was 40.1°C, IMD data showed.
Historically, the bulk of Delhi’s heatwave days fall between mid-April and early June. IMD records show no heatwave at Safdarjung in April last year, although five such days were logged in May. April 2023 remained heatwave-free too, but Delhi residents endured four hot days in April 2022.
The all-time high for April is 45.6°C, which was recorded on April 29, 1941.
Earlier this month, the IMD had forecast above-normal maximum temperatures in most regions across the country this April, except for some parts of western and eastern India. It had said the minimum would also be above normal in most regions in the country.
Meanwhile, Delhi’s pollution levels deteriorated further in the “poor” category, with a 24-hour average air quality index (AQI) reading of 261 at 4 pm on Monday. The average AQI was 209 (poor) at the same time a day earlier.
Forecasts by the Centre’s Early Warning System for Delhi (EWS) shows AQI should stay in the “poor” zone till April 9. It is expected to improve to the “moderate” category once again on April 10, aided by the approaching western disturbance and strong surface winds.
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