The IMD on Thursday warned of heavy rainfall in the sub-Himalayan areas of West Bengal and a few southern districts, due to an active monsoon trough and a cyclonic circulation over central Bangladesh.

The sub-Himalayan districts of Darjeeling, Kalimpong, Jalpaiguri, Alipurduar and Cooch Behar are likely to receive heavy rain till August 12, with very heavy rainfall at one or two places on August 11, it said in a bulletin.

In south Bengal, South 24 Parganas, Purulia, Paschim Medinipur, Bankura, Purulia and Purba Bardhaman are expected to experience heavy showers till August 9.

The IMD forecast an overcast sky with light to moderate rain in Kolkata till the morning of August 9, it said.

Heavy rainfall occurred at one or two places in Coochbehar, Jalpaiguri and Alipurduar districts of north Bengal in the past 24 hours till 8.30 am on Thursday, the IMD said.

The Gopalpur tea estate in Alipurduar and Damdim tea estate in Jalpaiguri district received 100-mm rain each during the period, the highest in the state, while Sankosh in Cooch Behar recorded 80-mm precipitation, the bulletin added.

Other northern districts—Cooch Behar, Uttar Dinajpur, and Malda—are under yellow alert, with forecasts of heavy rainfall (7-11 cm), gusty winds (30-40 kmph) and the possibility of lightning. The IMD has warned of waterlogging, inundation in low-lying areas, and reduced visibility.

In South Bengal, Kolkata, Howrah, Hooghly, and Nadia districts are under yellow alert for the next three days. Thunderstorms with gusty winds (30-40 kmph) and lightning are expected. Temporary waterlogging and traffic disruptions may occur, the IMD has cautioned, and people are advised to avoid open fields and contact with water bodies due to lightning risks.