‘Feels like 51.9 degrees Celsius’: Red Alert sounded as Delhi simmers, relief likely over weekend

However, senior IMD officials clarified, India does not officially validate or maintain records of the heat index, which is calculated based on a combination of temperature and humidity. “Heat index depends on temperature and relative humidity and varies throughout the day. But it is not validated under Indian conditions, and no formal records are maintained,” a senior official said.

A  yellow alert has been sounded for Friday, with conditions expected to ease from June 14 amid the possibility of rain. The maximum temperature is likely to range between 43°C and 45°C until Friday, the Met Office said.  A sporadic spell of rain is expected to prevail over the next six days in the city, with moderate rainfall forecast for June 16 and 17, potentially bringing some relief from the intense heat.

At the Safdarjung observatory, the city’s base weather station, the maximum temperature climbed to 43.3°C, 3.4°C above normal, on Wednesday.  The minimum temperature settled at 27.2°C, nearly a notch below normal.

At 45°C, the  Ayanagar weather station logged Delhi’s highest temperatures since mid-May, 3.5°C above normal, as it met IMD’s official threshold for heatwave classification. By contrast, Lodhi Road has consistently recorded the lowest daytime highs among city stations during the same period.

According to the IMD norms, a heatwave is declared when the maximum temperature is greater than or equal to 45°C, or when it is 4.5°C to 6.4°C above normal. If it crosses this range, it qualifies as a severe heatwave.

“From yesterday’s three stations reporting heatwave conditions, today only  Ayanagar has reported a heatwave. Temperatures are likely to remain in the same range tomorrow and are expected to see a gradual decline from June 13,” said an IMD official.

While there was a slight drop in daytime temperatures across the NCR over the past 24 hours, the night temperatures also showed a decline and were below or near normal.

In recent days, the Capital has also faced hot and humid conditions, another form of heat stress. The IMD sounds alerts for such conditions when daytime temperatures are three degrees above normal and relative humidity levels are significantly high.

On Wednesday, the humidity during the day fluctuated between 31% and 73%, and north-westerly winds blew at speeds of up to  18 kmph, according to IMD’s daily weather bulletin.