If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Manasota Key: The hottest months are usually July and August with an average temp of 82°F, while the coldest months are January and December with an average of 64°F. The rainiest months in Manasota Key are August, June, July, and September, with each month seeing an average of 7 inches of rainfall.