Weather will likely play an important role when you plan your trip to Guapi, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually March and April with an average temp of 77°F, while the coldest months are January and December with an average of 77°F. The rainiest months in Guapi are May, June, December, and January, with each month seeing an average of 37 inches of rainfall.