Sri Lanka is affected by two different monsoon seasons affecting opposite sides of the islands, so this makes the weather patterns quite complex. The Yala monsoon occurs between May and August affecting the south western part of the island, followed by a transitional period in September and a dry season between December and March. The Maha monsoon brings wet weather to the north east of the island between October and March, followed by a dry season between May and September. The driest time to visit the island can be in the inter monsoon periods of March/April and August/September, inland the Cultural Triangle's driest months are normally June/July/August. October and November can be quite wet months.
In the wetter seasons, rain normally occurs in short sharp downpours and there are many dry spells of sunshine, so can be a great time to take advantage of special offers. It’s worth noting that the basic patterns described can vary from year to year due to global warming.