Continuing bad weather forced President Mahinda Rajapakse to abandon a tour of flood-affected areas.
Many schools remained shut with the military deployed to rescue marooned villages and help distribute food, clothes, bedding and water, a spokesman for the Disaster Management Centre in Colombo told AFP.
Floods have also disrupted food supplies, with wholesale prices of vegetables rising sharply.
Sri Lanka depends on monsoon rains for irrigation and power generation, but the seasonal downpours frequently cause death and damage to property in low-lying areas.
The island's two main monsoon seasons run from May to September and December to February.