New areas in Faridpur, Munshiganj, Shariatpur, and Rajbarhi districts are going under water.
Hundreds of thousands of families are joining thousands more already affected by the flood.
Over 300,000 people got stranded in Shariatpur and Faridpur as new areas have started to be submerged in the districts.
According to the Flood Forecasting and Warning Centre, the river Padma was flowing 100 centimetres over the danger level at Goalanda point on Monday.
River erosion has continued at Daulatdia, threatening the ferry pier in the area and the roads towards it. The pier was closed four days ago.
The Department of Disaster Management says 21 persons have died in flooding in 16 districts that have been hit since mid-July.
The Directorate General of Health Services has put the number of deaths in the deluge at 42.
According to the government, around 634,500 families in the 16 districts have been affected by the flood. They have lost 8,140 houses to river erosion.