The Department of Meteorology said the northeast monsoon is gradually establishing over the island, bringing showers to Northern, North-Central, Eastern and Uva provinces, as well as Matale and Nuwara Eliya districts.
Other areas will experience showers or thundershowers after 1.00 p.m.
Fairly heavy rain of 50 mm or more is likely in Western and Sabaragamuwa provinces and in Galle and Matara districts.
Misty conditions are expected in Western, Sabaragamuwa, Central and Uva provinces during the early morning.
The public has been advised to take precautions against strong winds and lightning during thundershowers.