If you're hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Santa María Tonameca: The hottest months are usually April and March with an average temp of 78°F, while the coldest months are January and February with an average of 76°F. The rainiest months in Santa María Tonameca are September, June, August, and October, with each month seeing an average of 20 inches of rainfall.