Weather is probably a major factor when you plan your trip to Lago Sul, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually September and October, with an average temperature of 23°C, while the coldest months are July and June, with an average of 21°C. The rainiest months in Lago Sul are December, November, January and March, with each month seeing an average of 267 mm of rainfall.