The Disaster Management Center (DMC) says that 37 people have died and another 80 are missing in Kalutara District due to floods and mudslides triggered by heavy rain.
Meanwhile the death toll in the Ratnapura District has climbed to 28 so far, according to the DMC.
The Disaster Management Center said more than 7,800 persons are affected by the calamity.
Home Affairs Minister Vajira Abeywardana told reporters Friday that the adverse weather conditions in southern and western parts of the island could still worsen in the next 72 hours.
The National Building Research Organisation (NBRO) alerted the public to be vigilant on possible landslides in mountainous areas in Galle, Kegalle, Ratnapura, Kalutara, Matara and Hambanthota districts, Colombo Page reported.
Heavy rains have lashed several parts of the country since Thursday.
South-west monsoon conditions are establishing over the country. Hence, showery and windy conditions are expected to continue over the south-western part of the country.
The people living in low lying areas around Kelani River and Kalu Ganga are cautioned about possible floods.