According to the Department of Meteorology, the disturbance in the lower atmosphere in the south-east of Sri Lanka has now developed into a low pressure zone.
As it may develop further in the next 24 hours, rain conditions are expected to increase in most parts of the island.
The sky will remain cloudy in North, North Central and Eastern provinces.
Eastern, Uva, North and North Central provinces and Matale district will experience rain or thunder from time to time.
Rain or thundershowers will occur in the rest of the island during evening or night.
The department announces that 100 mm of heavy rain may occur in some places in North, North Central, East, Sabaragamuwa and South provinces.