Costa Rica's high season for tourism runs from late November to late April, which coincides almost perfectly with the chill of winter in the United States, Canada, and Great Britain, and includes Christmas, New Year's, Easter, and most school spring breaks. The high season is also the dry season. If you want some unadulterated time on a tropical beach and a little less rain during your rainforest experience, this is the time to come. During this period (and especially around the Christmas holiday), the tourism industry operates at full tilt -- prices are higher, attractions are more crowded, and reservations need to be made in advance.
Local tourism operators often call the tropical rainy season (May through mid-Nov) the "green season." The adjective is appropriate. At this time of year, even brown and barren Guanacaste province becomes lush and verdant. I personally love traveling around Costa Rica during the rainy season (but then again, I'm not trying to flee cold snaps in Canada). It's easy to find or at least negotiate reduced rates, there are far fewer fellow travelers, and the rain is often limited to a few hours each afternoon (although you can occasionally get socked in for a week at a time). A drawback: Some of the country's rugged roads become downright impassable without four-wheel-drive during the rainy season.
Costa Rica is a tropical country and has distinct wet and dry seasons. However, some regions are rainy all year, and others are very dry and sunny for most of the year. Temperatures vary primarily with elevations, not with seasons: On the coasts it's hot all year; in the mountains it can be cool at night any time of year. Frost is common at the highest elevations (3,000-3,600m/9,840-11,808 ft.).
Generally, the rainy season (or "green season") is from May to mid-November. Costa Ricans call this wet time of year their winter. The dry season, considered summer by Costa Ricans, is from mid-November to April. In Guanacaste, the dry northwestern province, the dry season lasts several weeks longer than in other places. Even in the rainy season, days often start sunny, with rain falling in the afternoon and evening. On the Caribbean coast, especially south of Limón, you can count on rain year-round, although this area gets less rain in September and October than the rest of the country.
In general, the best time of year to visit weatherwise is in December and January, when everything is still green from the rains, but the sky is clear.
Because Costa Rica is a Roman Catholic country, most of its holidays are church-related. The biggies are Christmas, New Year's, and Easter, which are all celebrated for several days. Keep in mind that Holy Week (Easter week) is the biggest holiday time in Costa Rica, and many families head for the beach. (This is the last holiday before school starts.) Also, there is no public transportation on Holy Thursday or Good Friday. Government offices and banks are closed on official holidays, transportation services are reduced, and stores and markets might also close.
Official holidays in Costa Rica include January 1 (New Year's Day), March 19 (St. Joseph's Day), Thursday and Friday of Holy Week, April 11 (Juan Santamaría's Day), May 1 (Labor Day), June 29 (St. Peter and St. Paul Day), July 25 (annexation of the province of Guanacaste), August 2 (Virgin of Los Angeles's Day), August 15 (Mother's Day), September 15 (Independence Day), October 12 (Discovery of America/Día de la Raza), December 8 (Immaculate Conception of the Virgin Mary), December 24 and 25 (Christmas), and December 31 (New Year's Eve).
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.