Like what was said earlier, Costa Rica is a tropical nation. Like all tropical nations, Costa Rica experiences two seasons: wet and dry.We've known so much about Costa Rica's dry season. It's the time to hit the beach, etc. But what about the wet season? If you're going to stay here for a few months or years, you have to know what happens in Costa Rica when it pours.
To give yo a guide, here's a rainy season map courtesy of Costa Rica Guide.
Link: Costa Rica Rainfall and weather map