Weather is probably a major factor when you plan your trip to Sao Joao da Boa Vista, and keep 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 temp of 72°F, while the coldest months are July and June with an average of 64°F. The rainiest months in Sao Joao da Boa Vista are January, December, November, and February, with each month seeing an average of 9 inches of rainfall.