Rain is on the way, the Met office said on Thursday.

“In view of favourable wind pattern and strong moisture incursion from Bay of Bengal, enhanced thunderstorm and associated activities very likely to occur over the districts of South Bengal during the next two to three days,” a Met bulletin said.

The city needs a formidable spell to cool down, even if briefly. A good spell is likely — up to 75% probability, said a Met official — on Friday, according to the forecast.

The sky was cloudy in parts on Thursday, causing a marginal drop in the day temperature. Partial relief from the heat and humidity began from Wednesday evening.

Some parts of the city received very light rain on Wednesday evening.

But the conditions had become breezy.

The Met office reported a squall in Alipore between 6.50pm and 6.52pm on Wednesday, with a peak wind speed of 60kmph.

Dark clouds over the city sky of Calcutta on Thursday evening

Thursday night was also breezy. Some districts, mainly in the west of south Bengal, got light rain.

While south Bengal has been praying for rain, north Bengal has been getting plenty. The change in wind patterns will now send more moisture into south Bengal, said Met officials.

“The upper air cyclonic circulation over north Jharkhand and the neighbourhood, a trough from northwest Uttar Pradesh to north coastal Andhra Pradesh are the active weather systems,” said an official.

On Friday, light to moderate rain or thundershowers across south Bengal is expected.

The intensity is likely to be on the higher side in East Midnapore, West Midnapore, Jhargram, Bankura and Purulia, the official said.

In north Bengal, the intensity and spread of the showers is likely to dip from Friday.

Any rain on Friday is likely to be accompanied by gusts of wind and streaks of lightning.

“We are nearing the end of the Nor’wester season,” the Met official said.