There's nothing like an all-inclusive vacation in Termas de Rio Hondo to rejuvenate you, especially when you know what to expect from the elements. Here's some info to help you decide when to book: 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. August and July are the driest months while January and February are the rainiest months.