The Patenga weather office recorded 94.6mm rainfall in the 24 hours to 3pm on Wednesday.
It began raining in the port city on Monday night and continued with brief pauses on Tuesday before getting heavier at night.
Incessant downpour all day through Wednesday disrupted traffic and movement of people in the streets of the city. Some people were forced to walk to their destinations to attend to emergencies amid the lockdown with fewer rickshaws on the streets in comparison with other days.
The Bangladesh Meteorological Department on Wednesday said the low over the north Bay and adjoining area now lies over southwestern part of Bangladesh and adjoining area as a well-marked low, and is likely to move northwestwards.
One of its associated troughs extended up to north Bay and monsoon is active over Bangladesh and strong over north Bay.
The Patenga weather office forecaster Biswajit Chowdhury said heavy downpour may occur over the next 24 hours with the low and monsoon active.
The Met Office also cautioned that heavy rainfall might cause landslides in some hilly regions of the Chattogram Division.
Meanwhile, the district administration has begun evacuating people from areas, including Batali Hill, Matijharna, Akbar Shah, Hill-1, Hill-2, Bayezid Link Road, that are all experiencing rainfall for three straight days, and moving them to the storm shelter.
Officials at the district administration along with members of volunteer organisations began the evacuation on Tuesday night.
As of Wednesday afternoon, as many as 310 individuals from 92 families have been moved to the storm shelter, said Executive Magistrate Md Umar Faruk.
Chattogram Deputy Commissioner Mohammad Mominur Rahman in a press release said the people brought into the storm shelter are being provided with food and first aid, with enough food is in reserves.
Kattali Assistant Commissioner (land) Md Enamul Haque told bdnews24.com that people residing in risky zones at Firoz Shah were evacuated at night.