Sri Lanka gets rain from two directions at two times of year. Whichever coast is being soaked, the other is dry, so something is always in season.
Yala · south-west
May – Sep
The south-west monsoon soaks the south and west coasts and the hill country. The east is bone-dry, and the surf season moves to Arugam Bay.
Wet · south & west coasts, hills Dry & prime · east coast, dry-zone parks
Maha · north-east
Dec – Feb
After the October–November inter-monsoon storms, which reach the whole island, the north-east monsoon turns and rains on the east and north. The south and west settle into their long, clear, dry-season peak.
Wet · east & north coasts Dry & prime · south & west