If you are planning to travel to Costa Rica soon, the wet or green season starts in May. This season lasts from May until November. This season generally discourages many tourists, due to all the rain, but it is the cheapest time to travel. There are many deals on hotels, and attractions have little crowds. Many areas in the interior of the country are unreachable by vehicle until the dry season, but there is still a lot to do.
Expect a lot of rain, as Costa Rica gets up to 25 feet of rainfall each year, mainly in the mountains. The most rain occurs during September and October. Generally, the best weather is during May and June of this period, but it depends on where you plan to travel. The weather on the Caribbean Coast never changes, and it stays slightly wet throughout the year. The Central Valley area, including San Jose, stays nice during this time period, too, with less rain than other areas.
During the wet season, stick to the beaches and the villages close to the beach. The mountains get the most rainfall, more so than anywhere else does. This would be a great time to head to the San Jose area to see the museums and art galleries there. Indoor activities are your best bet, but having a list of places you’d like to see near the coast is a good idea.