The city got more than one spell of rain on Wednesday as a low-pressure system on the Bay kept sending south easterly winds into south Bengal.
The spells were brief. The rain was often in the form of a drizzle. In the afternoon, a relatively sharper spell struck southern and central parts of the city.
The conditions remained overcast for the rest of the day.
"A low-pressure area has formed over central parts of north Bay of Bengal and now lies over northwest and adjoining westcentral Bay of Bengal. It is likely to become more marked during the next 24 hours and move across south Odisha and south Chhattisgarh during the next three days," said the daily weather report issued by the Met office.
Once the system moves to interior Odisha, the rain will go down in Calcutta, said a Met official.
"Calcutta is more likely to get rain while the system is on the Bay. The next 48 hours are likely to be cloudy in Calcutta. More than one spell is expected on both days. But the rain is not going to be heavy," said G.K. Das, director, India Meteorological Department, Calcutta.
The monsoon trough is also passing through south Bengal, leading to moisture incursion. But the trough is likely to rise in a day or two, said Das.
"The monsoon trough now passes through Digha and thence southeastwards to the centre of low-pressure area over northwest and adjoining westcentral Bay of Bengal," said the Met bulletin.
Between 8.30am and 5.30pm on Wednesday, the Met office recorded around 10mm of rain in Alipore.
Both July and August, the two rainiest months on the city's calendar, recorded significant rain deficits. But September has so far recorded a surplus in Calcutta, thanks to two back-to-back systems on the Bay.