If you're hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Lago Sul: The hottest months are usually September and October with an average temp of 74°F, while the coldest months are July and June with an average of 69°F. The rainiest months in Lago Sul are December, November, January, and March, with each month seeing an average of 11 inches of rainfall.