Because Costa Rica is located only eight degrees north of the equator, the climate is tropical year round. The mean annual temperature on the coastal lowlands is around 80°F (27°C) and below 50°F (10°C) on the summits of the highest mountains. There are no hurricanes, tropical storms, tornadoes or even cold fronts. If you were to tell someone the current temperature is in the low 80's with sunny skies, you would be right 99% of the time. (The local weathermen are still only 50% accurate.)

There are two "seasons" and the only real difference between the two is the amount of rainfall. The Green Season is from May to November. Rainfall and humidity is highest on the Caribbean side. It is not unusual for the Pacific coast to have beautiful sunny days with afternoon or evening showers. The peak month will only bring a total of about 12" of rain.
Weather Expectations
Costa Rica Boat Charter Pacific

Charter EcoQuest for a Pacific Cruise