Weather will likely play an important role when you plan your trip to San Isidro, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually September and May with an average temp of 79°F, while the coldest months are February and January with an average of 76°F. The rainiest months in San Isidro are January, October, June, and May, with each month seeing an average of 10 inches of rainfall.