A low pressure has formed over east central Bay and adjoining areas and is likely to intensify into a cyclonic storm, the met office said on Sunday.
The low pressure is likely to turn into a deep depression and then into a cyclonic storm, the Bangladesh Meteorological Department (BMD) said in a regular bulletin.
Trough of low lies over West Bengal and adjoining areas, the BMD said.
Maritime ports of Chattogram, Cox's Bazar, Mongla and Payra have been advised to keep hoisted distant cautionary signal number one.
All fishing boats and trawlers over North Bay and deep sea have been advised to come close to the coast and proceed with caution.
Rain, thunder showers accompanied by temporary gusty, squally wind is likely to occur at a few places over Barishal and Chattogram divisions in next 24 hours commencing from 9am on Sunday.
Rain may also occur at one or two places over Khulna, Dhaka and Sylhet divisions but the weather may remain mainly dry with temporary partly cloudy skies elsewhere over the country, met office stated.
Besides, mild to moderate heat wave is sweeping over Dhaka, Khulna and Barishal divisions and the regions of Rangamati, Sitakunda, Cumilla, Chandpur, Noakhali, Feni, Moulvibazar, Rajshahi and Pabna and it may abate from some places.
Day and night temperatures may fall slightly over the country.