A low-pressure area has formed over the North Bay and adjoining coastal areas of West Bengal and Bangladesh and it is likely to intensify, according to the Bangladesh Meteorological Department .
It forecast rains across all eight divisions in 24 hours commencing 9 am on Wednesday.
Light to moderate rain and thundershowers, accompanied by temporary gusty winds, are likely to occur at many places over Khulna, Barishal and Chattogram divisions and at a few places over Rangpur, Rajshahi, Dhaka, Mymensingh and Sylhet divisions.
Moderately heavy to heavy rainfall is also likely at places across the country, said a BMD bulletin.
Daytime temperatures may remain nearly unchanged, while nighttime temperatures could fall slightly across the country.
The axis of the monsoon trough extends through Rajasthan, Madhya Pradesh, Uttar Pradesh, Bihar, Gangetic West Bengal and the centre of the low-pressure area to Assam, crossing the southern parts of Bangladesh.
The monsoon is currently fairly active over Bangladesh and strong over the North Bay, the bulletin said.