The IMD has attributed the widespread rainfall to the monsoon trough stretching from southwest Uttar Pradesh through Jharkhand and West Bengal into the Bay of Bengal. A steady inflow of moisture from the Bay is strengthening rain-bearing clouds across the region.
A yellow alert has been issued for Kolkata and most districts of South Bengal through Monday, warning of heavy spells of rain at isolated places.
In North Bengal, conditions remain more severe. Districts including Darjeeling, Kalimpong, Jalpaiguri, Cooch Behar and Alipurduar are expected to receive heavy to extremely heavy rainfall over the coming days. Malda, Uttar Dinajpur and Dakshin Dinajpur are also likely to witness heavy showers.
The IMD has additionally pointed to an active cyclonic circulation over Bangladesh, which is expected to enhance rainfall over northern parts of the state.