Sri Lanka's Monsoon Calendar, Explained

Sri Lanka has two monsoons, and they hit opposite coasts at opposite times — which is why the island always has a dry beach somewhere.

West & South coasts (Negombo down to Tangalle): dry season runs November to April. The southwest monsoon brings rougher seas and more rain from May to September.

East & North coasts (Arugam Bay up to Jaffna): dry season runs May to September — the reverse. The northeast monsoon brings the wetter, rougher window from October to January.

Practically: if you're visiting December–March, stick to the west and south. Visiting July or August, head east — Arugam Bay's surf season and Trincomalee's calm water are both in full swing while the south coast is at its wettest.