The Disaster Management Centre (DMC) said that water levels of the Kelani river, the fourth largest river in the country and the Maha Oya that flows through five important districts, continued to rise as heavy rain lashed out in many parts of the country.
A DMC spokesman told Xinhua news agency that authorities were on alert and were ready to face any emergency situation if the rivers over-flowed.
Residents along the river banks were evacuated and housed at temporary camps.
The Meteorology Department said that heavy rain and strong winds would continue in many parts of the island country.
The extreme weather which began on Saturday was a result of an atmospheric disturbance in the vicinity of Sri Lanka and had intensified into a low pressure area.
Several roads in the country were cut off by minor floods and uprooted trees.
At least eight districts also issued landslide warnings.
Earlier on Monday, three international airlines which were scheduled to land at Sri Lanka's main international airport at Colombo, were diverted to India.