If you're looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in San Mateo Xoloc: The hottest months are usually April and May, with an average temperature of 18°C, while the coldest months are January and December, with an average of 14°C. The rainiest months in San Mateo Xoloc are August, July, September and June, with each month seeing an average of 186 mm of rainfall.