Weather will likely play an important role when you plan your trip to San Antonio, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually May and April with an average temp of 81°F, while the coldest months are January and February with an average of 75°F. The rainiest months in San Antonio are November, July, October, and August, with each month seeing an average of 14 inches of rainfall.