Weather is probably a major factor when you plan your trip to Termas de Rio Hondo, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually January and December with an average temp of 79°F, while the coldest months are July and June with an average of 60°F. The rainiest months in Termas de Rio Hondo are January, February, December, and March, with each month seeing an average of 10 inches of rainfall.