Costa Rica Weather
Although Costa Rica is considered to have a stable climate, it is important to note that different temperature and weather conditions may be experienced within the same day, or within short distances, due mostly to the rugged terrain of this mountainous country. There are two well defined seasons: the rainy season or winter (invierno), and the dry season or summer (verano), with basically one main difference between them: rainfall averages. Dry season runs from December to April, and the rainy season from May to November. Rainfall averages for the country may reach the highest point during the months of September and October — approximately 650 mm per month.
Seasonal changes don’t bring significant changes in temperatures, although nights may be cooler in some areas during the rainy season. Mornings will most commonly be sunny all year round. San José is located 1150 meters above sea level, and has a moderate temperature throughout the year. It may go as low as 59ºF at nighttime, and up to 78ºF during the day, giving rise to the image of San José as a city with an eternal spring climate. The Intermontane Central Valley where San José lies has an average temperature of 68ºF, and may actually be considered as dry compared to the humidity of the Caribbean Slope. When it rains, temperatures will drop slightly, mostly because of humidity and winds.
The Caribbean coastline has an average temperature of 70ºF at night, and 86ºF during the day. The rainy season has a rainfall average of 224 inches (5,600 mm) per year, along the coast, on the eastern face of the mountains and in the Caribbean lowlands. In most of Costa Rica the peak periods of rainfall occur during May to June and September to October, whereas in the Atlantic these are the driest months. Though it is considered to be the wettest region of the country, rains usually occur at late evening and nighttime. Due to humidity and trade winds, temperatures will remain low, and even drop noticeably during rainy nights.
The northern part of the Pacific coast, as well as Guanacaste, is totally dry for six months of the year. Rainfall averages only 59 inches (1,500 mm) a year in the northwest and central part of the country. The South Pacific region is wetter than its counterpart to the north. General rainfall will reach up to 197 inches (5,000 mm) a year. High mountainous areas, such as the region surrounding Costa Rica’s highest peak Cerro Chirripó, have cold, windy and cloudy conditions all year round. Chirripó remains below 50ºF during the day, and may experience temperatures as low as 32ºF at night. Frost and even snow have been reported. During early morning hours, Costa Rica’s highlands usually reach below-freezing temperatures.
As a general rule, temperatures decline with elevation at a rate of approximately 3.5F per thousand feet in Costa Rica. Thus, average December temperatures vary from 79ºF at Orotina on the coast, to 66ºF in San José at 3.500 feet, to a chilly 43ºF in Villa Mills at 10,000 feet.
First-time visitors to Costa Rica often neglect to bring a warm jacket with them after reading about the climates of the coastal regions and the Central Valley. A medium-weight fleece jacket is ideal.