The bodies of 30 fishermen plus one victim on land have so far been recovered while another 31 fishermen caught in rough seas are missing, said a spokesman for the Disaster Management Centre (DMC).
The rain and winds which hit the island early on Saturday have also destroyed more than 100 houses and damaged another 2,185 buildings, said the spokesman, Sarath Lal Kumara.
"We continue to look for missing people," Kumara told AFP. "The navy and the air force are leading the search and rescue operations.
Another 35 people have been injured by the storm.
A group of Buddhist monks has lodged a protest with the Colombo meteorological office, accusing it of failing to alert people early enough about the strength of the monsoon.
"Your inefficiency resulted in a national calamity," the monks said in a letter addressed to the head of the office.
"We demand that you take every step possible to prevent a recurrence.
There was no immediate comment from the met office. The monsoon hits