In Sri Lanka, May is off season. Of course this is bad news for tour operators, as we have only few bookings, for example from Arabian families, as May or June are school holidays in Gulf countries. However, for travellers who are intersted to visit the southwestern beaches between Colombo and Galle and who free to choose the month of May, we recommend May, not only for our own advantage but also for our coustmers': The beaches are less crowded.
In contrast, those travellers interested in sightseeing in the Cultural Triangle should know that May (besides October) is the peak of precipitation in Anuradhapura and our hometown Mihintale and has most rainy days. Roughly, rainfall occurs every second day, but usually it's not raining the entire day.
Nuwan Chinthaka Gajanayaka