There was the danger of the banks of some rivers bursting while minor floods were experienced in most parts of the country, the Disaster Management Centre (DMC) said, adding that its 25 centres countrywide were working round the clock with the support of the tri forces and health officials to face any eventuality.
Nearly 3,000 people were affected by heavy rains and floods on Saturday, one person in Kegalle died in a slope cutting failure and another in Galigamuwa drowned.
The DMC said banks of many rivers such as Kalu Ganga could burst.
The National Building Research Organization (NBRO) has said that landslide risk warnings in Galle, Matara, Matale, Ratnapura, Kalutara, Kegalle, Colombo, Nuwara Eliya, Kurunegala and Kandy remained valid.
The NBRO urged residents to be vigilant about the possibility of landslides, slope failures, rock falls, cutting failures and ground subsidence, if the rains continue.
DMC spokesman Pradeep Kodipilli said that minor floods were also experienced in several areas across the country including in Kegalle.
The Department of Irrigation forecasts that the Giriulla – Kurunegala road could become inundated if the rains continue. The Kelani Ganga water level is also rising in the Holombuwa area. The water level of the Attanagalu Oya too is reaching dangerous levels in the Dunamale area. Residents in low lying areas of the Kalu, Kelani, and Gin rivers have been asked to remain vigilant.
The people living in low lying areas close to the basins of Mee Oya, Deduru Oya, Attanagalu Oya, Kelani, Kalu, Bentara, Gin and Nilwala rivers, Kirama Oya and Uruboku Oya have also been advised to be vigilant about the rising water levels.
Showers or thundershowers will occur in Southern, Western, Sabaragamuwa and Central provinces with isolated very heavy showers exceeding 150mm. Showers or thundershowers will occur elsewhere particularly in Uva and Eastern provinces in the evening or night.
The Fishing and naval community are requested to be vigilant as the sea areas around the island can be fairly rough and the sea area extending from Colombo to Pottuvil via Galle and Hambantota will be rough to very rough at times. Temporarily strong gusty winds up to 70-80 kmph and very rough seas can be expected during thundershowers.
Naval and fishing communities have been advised not to venture out to sea until further notice due to adverse weather created by a low pressure system in the Bay of Bengal.
DMC also said that the Met Department low pressure system that has developed in the sea off the South-East of the Bay of Bengal could bring thundershowers in the shallow and deep seas around the island. The Met Department also warns that wind speeds could suddenly increase between 60-70 kilometres per hour.
The Met Department also warns that seas could rise up to 2-2.5 metres along the coast from Mannar to Colombo, Galle, Hambantota and up to Pottuvil. This could result in waves coming ashore.