The city received close to 150mm of rain between last Monday and Friday, more than the usual quota of entire May.

The mean monthly total rainfall that Calcutta gets in May is 118.5mm. The volume is calculated based on figures collected by the Met office between 1991 and 2020.

This year, Calcutta and the rest of south Bengal were scalded by what was one of the most brutal and lengthy heat assaults in years.

In Calcutta, the scorching spell ended on May 6, when a thunderstorm triggered around 50mm of rain in Alipore. On May 9, the city got around 60mm of rain.

Between May 6 and 10, the Met office recorded around 145mm of rain.

But the conditions are set to change. The showers are now likely to be on the wane. One or two spells of thunderstorms are not ruled out on Tuesday and Wednesday, but the weather is likely to be dry from Thursday. The days are likely to be scorching again.

“The wet spell was caused by favourable weather systems and strong moisture incursion from the Bay. Now, the conditions are changing again. The moisture incursion is likely to go down. The wind pattern is also changing. Hot and dry westerly winds are likely to replace the moisture-laden southerly winds in the lower atmosphere,” said H.R. Biswas, head of the weather section at the Regional Meteorological Centre, Calcutta.

“A spell of thunderstorm and rain is not entirely ruled out in Calcutta till Wednesday. But after that, a dry spell is likely. The day temperature is likely to reach 37 degrees by the weekend.”

The maximum temperature in Calcutta was 34.2 on Monday. “There will be some humidity on the surface of the earth. That will multiply the discomfort index. But the lack of humidity in the lower levels of the atmosphere will prevent the formation of rain clouds,” said a Met official.