The best time to visit Costa Rica is in the latter halves of April and November. During these times Costa Rica experiences its least rain and small crowds. These times act as transition periods between the dry and rainy seasons to provide visitors with greenery and clear skies.
The dry season generally starts in mid-November and lasts until mid-April. February and March are popular months to visit Costa Rica because they fall within the borders of the dry season. September and October are also great months to visit because of hotel deals and diminished crowds.
These months fall in the rainy season when, most often, the mornings are sunny and dry, rain falls for a couple of hours in the afternoon, then the skies clear again. September and October are not good for whitewater rafting on the Pacuare River or visiting Corcovado National Park. Heavy rain makes the rapids unsafe and floods trails in the rainforest park.
Learn more: Best Time to Visit Costa Rica