Sri Lanka is a tropical country with almost the same season all year long except for monsoon seasons kicking off at different times during the year, despite showers a warm sunny climate is always guaranteed.
It's a year-round destination, and even during the monsoon periods, the weather is not consistently wet. The weather doesn’t run like clockwork here, and you can always be surprised in Sri Lanka! There are some rules to bear in mind though, to work out the best time for you to visit, but they do depend on where you want to go and what you want to see and do while there.
In a nutshell, the best time to visit the west and south coasts and hill country is from December to March, while the best weather on the east coast is from April/May to September.