The city was consistently cloudy and got light but persistent rainfall on Sunday.
Met officials said the overcast conditions would prevail for the next three days.
The Met office recorded around 17mm of rain between Saturday night and Sunday night in Alipore, which serves as the official recordkeeper for Kolkata.
“The monsoon trough is passing through Malda to the Northeast. Under its impact, rain-bearing clouds are taking shape over Bangladesh and adjoining Bay of Bengal. The clouds are moving towards Kolkata,” said G.K. Das, director, India Meteorological Department, Kolkata.
“The trough is likely to descend and come close to Kolkata on Monday. It is likely to remain active through south Bengal for a few days. The city is likely to get moderate rainfall in the next 72 hours,” said Das.
Around 60mm of rain over 24 hours is considered moderate.
The monsoon trough is an imaginary line connecting various low-pressure points from west to east. The monsoon trough keeps oscillating. When it is over the foothills of the Himalayas, north Bengal and the Northeast get rain. When it descends to the northern Bay of Bengal because of a low-pressure system, coastal Bengal receives rain. If the trough descends further, peninsular India gets drenched.
“The monsoon trough now passes through Amritsar (Punjab) Yamuna Nagar (Haryana), Bareilly (Uttar Pradesh), Gorakhpur (Uttar Pradesh), Patna (Bihar), Malda and thence eastwards towards Manipur,” said the daily weather report issued by the Met office.
In Kolkata, Sunday was cloudy to start with and stayed that way. The sun barely made an appearance and the maximum temperature dipped to 28.7 degrees, three notches below normal.