As more towns and villages are hit by floodwater, the number of people in state-run shelters had risen to 236,000 by Saturday evening, the Disaster Management Centre in Colombo said.
The homes of 1,053,000 people have been inundated, it said.
Police figures showed that at least 14 people had been killed in flood-related incidents in the past week.
Roads and fields were submerged across the east, centre and north of the island, with the torrential rains hampering rescue efforts. Authorities have issued a landslide alert in the central highlands and declared a state of emergency in some areas.
Last month 43 people were killed by floods in the same regions and the number of people driven from their homes also passed one million.