There was finally some respite from the sultry spell of the past 10 days, as Calcutta and its neighbouring areas received light rainfall on Wednesday evening.

Met officials said the 4.1-mm rainfall, triggered by a Nor’wester, dragged down the comfort index that shot up to 65.6 degrees at 11.30am, more than 10 degrees above normal.

“We are expecting rain on Thursday, too,” said G.C. Debnath, director of the weather section at the Regional Meteorological Centre, in Alipore.

The day’s maximum temperature was 35.6 degrees, a degree above normal, and the maximum humidity was 85 per cent.

The director explained that a trough of low pressure over Gangetic Bengal was sucking in moisture from the Bay of Bengal. “The trough helped form massive columns of clouds over Calcutta since the afternoon. We are also expecting thunder squalls in districts like Burdwan, Birbhum, Hooghly and the two Midnapores,” said Debnath.

The weather condition, he pointed out, is favourable for the monsoon to reach the northeastern states in the next couple of days. “But I cannot guess when it will arrive in Calcutta or the rest of south Bengal. The picture will become clearer in the next few days,” he added.

It’s unlikely that the monsoon will reach the city on June 8, the scheduled date of its arrival. A depression or cyclone over the east-central Bay could help drag in the current faster.