Costa Rica has two basic seasons, the summer and winter, also known as the dry season and rainy season, or for the tourism industry it’s called the high season and the low season. The tourism industry in recent years has adopted the phrase “green season” in place of “rainy/low season” simply because it rings infinitely more pleasant (a more true) than the words “rainy” and “low”. Increasing numbers of visitors to Costa Rica are realizing that the green season is a wonderful time to visit, when prices are low, crowds are sparse, and folliage is brilliant.
The attraction of the summer high season for travelers is the weather. Summer in Costa Rica runs opposite from North America and Europe, lasting from December to April, and many travelers come to the country to escape the dark slush of northern hemisphere winters and get a few more hours of daylight. During these months the northwestern province of Guanacaste and the Nicoya Peninsula gets the hottest and dryest of all of Costa Rica, and surf is at its best as storm swells in the Pacific create very attractive and reliable waves.
Winter/rainy season in Costa Rica is a lot less wet and rainy than many people assume, and generally lasts from May to November. Much of the country will receive impressive downpours in the early morning or afternoon, and the rest of the day receive brilliant sunshine. Folliage blooms like the best days of Spring, and the country becomes impressively green and lush. Many Costa Ricans prefer the early months of winter over any other time of year. Although the rainforest and cloudforests of Costa Rica will receive drenching rain during the winter, the beaches will continue to receive great weather. Some areas receive enormous amounts of rainfall during the depth of the rainy season, particularly the northeast and southwest. The Osa Peninsula, home to the largest tract of lowlying rainforest in Central America, receives such torrential downpours during September and October that reliable travel can become all but impossible, and many lodges will just close during those months.