One thing about Costa Rica that is truly amazing, is the micro climates that can be found along the country. If you are in San Jose downtown, you may be experiencing hot weather, but just 25 kilometers from there, you get to Cartago and have chilly weather with a little of rain. You go 2 hours in a road to a wonderful beach and in just 15 minutes you are in a mountain again with foggy weather.
This pictures shows a little bit of this, rain a sun coexisting in just the same landscape.