Sri Lanka Surf Guide
The surf on the South Coast
Surf spots on Sri Lanka‘s South Coast work from about October thru April. It's pretty much constant 3-5ft long-period clean swell with occasional bigger days. Its the tropics, so winds are gentle offshore every morning. It glasses off in the afternoon and goes offshore again in the evening. And the water is tropical Indian Ocean warm!
In the monsoon season - May thru September - it is offshore on the East Coast. Arugam Bay and other points around there work at this time.
On the South Coast during monsoon you can also find waves at protected points like Mirissa.
So there is good surf in Sri Lanka year-round.