For the past several days, the Met office had been issuing heatwave bulletins, each of them extending the duration of the scorching conditions.

On Friday came a bulletin that said: “Due to favourable wind pattern at lower levels and strong moisture incursion from Bay of Bengal, thunderstorms with lightning along with gusty wind speed activity very likely to occur over north Bengal from May 4 and over south Bengal from May 5.”

Calcuttans and people across the state are pinning their hopes on the thunderstorms to bring relief from the unrelenting assault of the sun that they have had to endure for days.

“The thunderstorms are likely to start in some districts on May 5. They are likely to spread across south Bengal and last till May 9. Calcutta is most likely to get thunderstorms on May 6 and 7. But they are not ruled out on May 8 and 9,” said a Met official.

Birbhum, Murshidabad, Nadia, North and South 24-Parganas and East Midnapore districts are likely to get thunderstorms on May 5.

The Met office recorded a maximum temperature of 39.2 degrees in Alipore on
Friday. It was still four notches above normal.

The conditions are likely to remain sultry till the storms strike.

The heatwave is likely to continue in Bankura, Birbhum, Murshidabad, Nadia, Jhargram, West Midnapore and East and West Burdwan districts till June 5, the Met bulletin on Friday said.

The start of April was marked by the beginning of this year’s first hot spell. It
saw heatwave conditions in some districts where the Celsius crossed the 40-degree mark.

The season’s first thunderstorm alert came on April 6, predicting rain, winds and lightning in Calcutta and the rest of south Bengal over the next couple of days.

Some districts got thunderstorms but Calcutta had to do with overcast conditions and a drizzle or two here and there. But the conditions dragged the Celsius down by several notches.

“As the moisture-laden southerly winds from the Bay gain momentum, the minimum relative humidity is likely to increase and stay between 40 and 50 degrees. For a substantial part of the day, the relative humidity is likely to be over 55 per cent,” said H.R. Biswas, head of the weather section at the Regional Meteorological Centre, Calcutta.