If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Thatch Caye: The hottest months are usually September and August with an average temp of 81°F, while the coldest months are January and December with an average of 76°F. The rainiest months in Thatch Caye are June, October, September, and August, with each month seeing an average of 10 inches of rainfall.