Weather will likely play an important role when you plan your trip to Santo Tomas, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually May and September with an average temp of 80°F, while the coldest months are February and January with an average of 77°F. The rainiest months in Santo Tomas are January, May, June, and October, with each month seeing an average of 8 inches of rainfall.