Unequivocally this question can not be answered, as Sri Lanka has several regions that differ sharply in climate

In May, the rainy season begins in the southwestern part of the island. This is due to the presence of the Central Mountain Massif, which creates a "rain shadow". Rains are strong and short (usually within 15 minutes) and are mostly at night. In general, the air temperature is around 32 degrees Celsius, the water temperature is 28 degrees.

The most favorable time for rest in Sri Lanka is from November to March, during this time the rains will not exactly bother you.

Will definitely be on the south coast of the island. In the east will not be