Mercury jumps to 43.4°C as fresh heatwave predicted to grip Delhi

The maximum temperature in Delhi inched up for the second straight day on Monday, even as a heatwave ensnared some neighbourhoods, with the weather department forecasting that the mercury will surge to 45°C in a couple of days.

Safdarjung, Delhi’s base weather station, clocked a maximum temperature of 43.4°C, 3.5 degrees above normal, up from 42.5°C on Sunday and 41.1°C on Saturday.

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According to the India Meteorological Department (IMD), the temperature at Safdarjung could rise to 44°C on Tuesday and 45°C on Wednesday.

Narela was the hottest area in Delhi, with a maximum of 46.6°C, followed by Najafgarh (46.3°C), both more than six degrees above normal.

IMD declares a heatwave in the plains if the maximum is 40°C or higher, while also being 4.5°C or more above normal. A “severe heatwave” is declared if it is 6.5°C or more above normal.

Monday’s dry heat meant Delhi’s Heat Index (HI) or “real-feel” was not significantly higher than the actual maximum on the day. The HI was 44.5°C on Monday, IMD’s bulletin said, up from 41.5°C a day earlier. Delhi’s wet-bulb temperature, another indicator of discomfort levels, was between 23.3°C and 23.8°C. A wet-bulb temperature of 32°C or higher makes it difficult for even fit and young people to work outdoors for long and at a wet-bulb temperature of 35°C — the maximum threshold — humans can no longer regulate body temperatures, leading to heat strokes and potential collapse.

In Delhi, this tends to be over 30°C, usually in July and early August, when temperatures are high and there is moisture intrusion, due to the southwest monsoon.

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This season, Delhi was first hit by a heatwave spell from May 17-20, before moist easterly winds brought in some respite.

Then, an unforgiving 12-day heatwave spell took hold between May 25 and June 5. During this time, the maximum rocketed to 46.8°C at Safdarjung on May 29 — the second-highest maximum for the station in May, behind the all-time high of 47.2°C, on May 29, 1944.

The highest maximum at any Delhi station this season is 49.9°C, recorded at north Delhi’s Narela on May 28.