Costa Rica has a subtropical climate. Lowland temperatures on the coasts average between 80 and 90 degrees during the day and a bit cooler at night. In the area around San Jose the daytime temperature is typically in the 70s, while higher up in the mountains the temperature can drop down into the 50s. The predictability of the dry season and wet (or “green”) season has changed a bit over the past few years, but traditionally the dry season is from late December through April.
The wet season can be a very good time to visit, as it won’t generally rain all day long. Instead it will rain for a couple hours in the afternoon and be clear for much of the day. July also has a fairly predictable dry spell that is called the “little summer.” During the wetter months there is the advantage that the country is especially green and lush, prices are lower, and there are fewer other tourists.
The weather patterns depend on the part of the country as well. December to April is usually rainless on the Pacific Coast, but this is when it rains most on the Caribbean coast. The dry season on the Caribbean coast is September and October. The Guanacaste Coast, including Tamarindo Beach, is the driest part of the country and generally has less rainfall throughout the year, including in the “wet” season.
The ocean temperatures on both coasts are usually around 74 degrees, which is very comfortable for swimming.