Planning for the weather is a good way to make your trip to Unawatuna relaxing and enjoyable, especially when you're splurging. The hottest months are usually March and April with an average temp of 81°F, while the coldest months are January and February with an average of 80°F. The rainiest months in Unawatuna are May, November, September, and October, with each month seeing an average of 13 inches of rainfall.