Weather will likely play an important role when you plan your trip to Piracicaba, 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 74°F, while the coldest months are July and June with an average of 66°F. The rainiest months in Piracicaba are January, December, February, and November, with each month seeing an average of 9 inches of rainfall.