If you're hoping to get lost in the rain on your romantic getaway, take a look at these details about year-round temperatures in Tecpan Guatemala: The hottest months are usually March and April, with an average temperature of 16°C, while the coldest months are January and December, with an average of 16°C. The rainiest months in Tecpan Guatemala are June, September, May and August, with each month seeing an average of 472 mm of rainfall.