For a relatively small island, Sri Lanka’s climate varies considerably,, choosing the best time to visit really depends on which part of Sri Lanka you want to visit. There are 2 monsoon seasons – the north-east monsoon can affect the whole island, bringing wind and rain from October to January. The less intense south-west monsoon impacts the south and west coasts, as well as the Hill Country between May and September. Coastal temperatures stay above 25°C year-round, whereas the Hill Country is generally cooler due to its altitude. The best time to visit the west and south coasts is between December and April, while May to October is the best time to visit the east coast.weather.