The soaring Celsius has prompted the Met office to issue a heatwave alert for the districts of south Bengal.

This is the third such spell this summer, an indication of how such unusual weather events have become more frequent.

Calcutta spent a sweltering Friday with the humidity playing a perfect foil to the soaring Celsius.

The Met office recorded a maximum temperature of 38.1 degrees Celsius in Alipore. It was a couple of notches above normal.

In districts like Bankura and Purulia, the Celsius touched 40 degrees and is likely to go further up.

On Saturday and Sunday, a heatwave is likely in districts like West Burdwan, Bankura and West Midnapore, according to the weather report issued by the Met office in Alipore on Friday.

Birbhum, East Burdwan, Bankura, Purulia, Jhargram and Murshidabad are among the districts where the conditions are likely to be “hot and humid”.

Calcutta might not be as scorching as these districts but will have a high discomfort index because of the combination of heat and humidity.

Some relief is expected in the form of thundershowers on Monday, according to the Met forecast. In the districts, thunderstorms are likely on Sunday, Monday and Tuesday.

“The cyclonic circulation over south Bihar and neighbourhood at 0.9km above mean sea level has become less marked. The cyclonic circulation over south Bangladesh at 1.5km above mean sea level has become less marked,” the weather report said.

“At the moment, the synoptic situation does not offer hope of any significant respite from the sultry conditions.”

Around 3pm on Friday, the temperature was around 38 degrees and the RealFeel was as high as 46.

Fans hardly made a difference and AC machines at full throttle were the only solace. The roads were reasonably less crowded in the afternoon.

The start of April was marked by the beginning of this year’s first hot spell. It saw heat-wave conditions in some districts where the Celsius crossed the 40-degree mark. Calcutta and the remaining areas of south Bengal were in the grip of sultry conditions.

Another heatwave had south Bengal, and Calcutta, in its grip from the third week of April. It was a prolonged spell, one that saw the Celsius touch and breach the 40-degree mark in Calcutta on several days.

The scorching spell was finally broken by a spell of formidable rain on May 6.