Weather will likely play an important role when you plan your trip to San Martin de las Pirámides, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually April and May with an average temp of 65°F, while the coldest months are January and December with an average of 58°F. The rainiest months in San Martin de las Pirámides are August, July, September, and June, with each month seeing an average of 7 inches of rainfall.