Weather is probably a major factor when you plan your trip to Porto Belo, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually February and January with an average temp of 75°F, while the coldest months are July and August with an average of 63°F. The rainiest months in Porto Belo are January, February, March, and December, with each month seeing an average of 7 inches of rainfall.