The city was lashed by a sharp spell of rain on Wednesday evening.

More rain is likely on Thursday and the weather is set to improve from Friday, the Met office said.

Wednesday was uniformly cloudy and many parts of the city received an intermittent drizzle in the first half.

By 5pm, the sky was ominously dark. Around 5.15pm, the Met office issued an alert of an “intense spell” of rain in East Midnapore, Calcutta, Howrah and North and South 24-Parganas.

The rain started minutes later. In many parts of the city, the showers reduced visibility. Traffic crawled on major thoroughfares. A ride from Esplanade to St Xavier’s College on Park Street took over 30 minutes, almost three times the usual time.

Between 5pm and 7pm, Mominpore received around 35mm of rain, Taratala got 31mm, Ultadanga got 27mm and Jodhpur Park got 26mm, figures obtained from drainage pumping stations of the Kolkata Municipal Corporation showed.

The overcast conditions were triggered by two systems.

“A low-pressure area over westcentral and adjoining northwest Bay of Bengal off north Andhra Pradesh-south Odisha coasts moved west-northwestwards and has become less marked,” said a Met bulletin.

“A trough runs from north Konkan to south Bangladesh,” it said.

A Met official told Metro: “The trough runs via south Bengal, close to Calcutta. The trough is more impactful than the low-pressure area.”

The overcast conditions dragged the Celsius down.

The maximum temperature on Wednesday was 28.1 degrees, four notches below normal. On Sunday, it was almost 35 degrees.

The Met official said “one or two spells” were expected in Calcutta on Thursday as well.

“The sky will start clearing from Friday,” he said.

The Met bulletin predicted heavy rainfall (7-11cm) in Purulia, West Burdwan, Birbhum and Murshidabad on Thursday.

The districts of north Bengal are likely to be lashed by “heavy to very heavy rain” on Thursday and Friday, the bulletin said.