A low-pressure area has formed over Northeast Bay and the adjoining area, intensifying into a well-marked low over the same area.
Under its influence, deep convection is continuing over North Bay, said a met office release issued at 11am on Saturday.
All maritime ports have been advised to keep hoisted local cautionary signal No three.
Southwest monsoon has advanced up to Chittagong and Sylhet divisions.
Rain and thundershowers accompanied by temporary gusty and squally wind are likely to occur at many places over Barisal, Chittagong and Sylhet divisions, at a few places over Dhaka, Mymensingh and Khulna divisions, and at one or two places over Rajshahi and Rangpur divisions, with moderately heavy to heavy falls at places over Barisal, Chittagong and Sylhet divisions in the next 24 hours, said the release.
Meanwhile, the highest rainfall in the last 24 hours till 6am on Saturday was recorded at 84mm in Tangail.
A mild heat wave is sweeping across the districts of Rajshahi, Pabna and Chuadanga and it may abate.
The highest temperature on Friday was recorded at 37°C in Chuadanga.
Day and Night temperatures may remain nearly unchanged over the country.
South-west monsoon may advance up to the central part of Bangladesh, the met office said.
