If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Deniyaya: The hottest months are usually March and February with an average temp of 76°F, while the coldest months are January and February with an average of 76°F. The rainiest months in Deniyaya are November, October, May, and September, with each month seeing an average of 17 inches of rainfall.