A squall on Friday evening briefly promised to pour healing rain on heat-scorched Calcutta, only to blow over without bringing so much as a drizzle.

Dust flew, trees fell and many Calcuttans heard (or imagined) the rumble of thunder in the distance as the squall whipped through the city around 8pm. Then everything fell quiet. Gone in 60 seconds.

But after 13 rainless days on the trot, this city has learnt to hunt for hope in meteorological despair. The Met office has forecast rain and thundershowers over the weekend, saying the Friday teaser that didn’t translate into a torrent wouldn’t affect the big weather picture.

“The trough of low pressure extending from Jharkhand to the West Bengal coast has strengthened, leading to the incursion of moisture from the Bay of Bengal and formation of clouds that are likely to bring rain to Calcutta and its surrounding areas,” said Gokul Chandra Debnath, the director of the Regional Meteorological Centre in Alipore.

The Celsius settled at 37.4 degrees on Friday, a slight dip from Thursday’s 38.1, but humidity didn’t drop below the mid-fifties throughout the muggy day. “The sun was a little less severe than yesterday but the stifling feeling was still there. I was bathed in sweat during a taxi ride from Theatre Road till Ultadanga around noon,” said life insurance executive Tuhin Bandopadhyay.

Wednesday was the hottest day of the season with the maximum temperature hitting 40.5 degrees Celsius, contrasting with a sharp drop in the minimum relative humidity to 28 per cent.

“Rain is the only answer to the discomfort caused by the two extremes of humidity, but the weather is unlikely to stay pleasant for long,” a Met official said.

Calcutta has had an unusually rain-deficient May this year with just two showers against an average of eight in the month over the past few years.

The last time it rained in the city was on May 4, which makes this the longest gap in five years.

According to Met records, the city receives 136mm of rain on an average in May. This year, more than half the month has passed with only 51.6mm of rain being recorded.