Costa Rica is located deep within the tropics, just 10 degrees north of the equator, resulting in a consistent, warm climate year-round. Temperatures do not vary widely; instead, the climate is defined by fluctuations in rainfall. The country’s diverse geography, featuring a mountainous spine separating the Pacific Ocean and Caribbean Sea, creates distinct, highly localized microclimates across a relatively small area.
The Defining Wet and Dry Seasons
The climate across much of Costa Rica is divided into two main periods defined by precipitation. The dry season, known locally as verano or “summer,” typically runs from December through April. Travelers can expect consistently sunny days with minimal rainfall, particularly in coastal areas. Temperatures remain warm, often ranging between 75°F and 95°F in the lowlands.
Following the verano is the wet season, referred to as invierno (winter) or the “green season,” which extends from May to November. This period is characterized by substantial rainfall, which revitalizes the country’s rainforests. The rain does not usually fall continuously; instead, mornings are often clear and sunny, with heavy, predictable showers occurring in the late afternoon or early evening.
The green season experiences its peak in rainfall during the months of September and October, especially on the Pacific side of the country. Even during this peak, the pattern of morning sun and afternoon rain often holds true, allowing for outdoor activities earlier in the day. The transition months of May and November can be less predictable, acting as a bridge between the two seasonal patterns.
The terms dry and wet season are most accurately applied to the Pacific side and the Central Valley, where the annual cycle is clearly delineated. The entire country receives a high average annual rainfall, around 100 inches, but the distribution of this precipitation defines the seasons. The change in seasons is marked by a shift in moisture, not a significant drop in temperature.
Regional Climate Divisions
The country’s central mountain ranges create a significant barrier, resulting in highly regionalized weather patterns along the two coasts. The Pacific Coast, which includes popular destinations like Guanacaste and the Nicoya Peninsula, experiences the most defined dry season. The northern portion of the Pacific side is the driest region in the entire country, with a dry season that can last up to six months.
Moving south along the Pacific coast, the duration of the dry season shortens, and the overall annual rainfall increases dramatically. The South Pacific, particularly the Osa Peninsula, is one of the rainiest regions, with a much shorter dry period from January to March. The Central Pacific region, including areas like Manuel Antonio, offers a balance, with a standard wet season from May to November and a hot, dry period otherwise.
The Caribbean Coast, stretching from Tortuguero to Puerto Viejo de Limón, does not follow the same seasonal calendar as the Pacific side. This region is generally wetter and more humid year-round, lacking a pronounced dry season. Rainfall totals are substantial, but the Caribbean experiences two relatively drier periods, typically in February and March, and again in September and October.
The drier window for the Caribbean Coast in September and October often coincides with the peak of the rainy season on the Pacific side, a phenomenon that offers a unique travel opportunity. This weather division is largely due to the effect of the trade winds, which push moisture onto the Caribbean slope for much of the year, while the mountains create a rain shadow effect for the Pacific coast during the dry season.
Temperature Variation Based on Altitude
Temperature in Costa Rica is primarily regulated by elevation. Lowland coastal areas are consistently hot and humid, with temperatures averaging between 77°F and 90°F throughout the year.
As elevation increases, the temperature decreases at a rate of approximately 3.5°F for every 1,000 feet of ascent. The Central Valley, which includes the capital city of San José, sits at an elevation between 3,000 and 5,000 feet above sea level. This altitude results in a pleasant, temperate climate often described as “eternal spring,” with average temperatures ranging from 65°F to 80°F.
In the high-altitude central mountain ranges, such as the areas around Monteverde or the Talamanca Mountains, the climate becomes noticeably cooler and often misty. At elevations above 5,000 feet, temperatures typically drop to between 45°F and 70°F, creating the cool, damp conditions necessary for cloud forests.
Unique Weather Phenomena and Travel Advice
The El Niño-Southern Oscillation (ENSO) cycle significantly influences Costa Rica’s weather patterns, creating deviations from the typical seasonal averages. During an El Niño event, the Pacific waters warm, which generally leads to drier conditions on the Pacific coast and in the Central Valley, especially during the wet season. This can result in drought-like conditions, impacting agriculture and leading to higher risks of wildfires.
Conversely, the La Niña phase, characterized by cooler Pacific waters, often increases the intensity and frequency of rainfall on the Pacific side of the country. This can heighten the risk of flooding and landslides in low-lying areas. The effect of these phenomena is complex, sometimes resulting in a drier-than-average Caribbean slope during a La Niña event.
While Costa Rica is situated in the broader Caribbean region, its geographical position and the influence of ocean currents mean it rarely experiences a direct hit from a hurricane. The Caribbean coast, however, is susceptible to heavy rains and strong winds from tropical storms and depressions that pass nearby, particularly late in the Atlantic hurricane season. Travelers should generally consider the months of September and October as the best time to visit the Caribbean coast for the highest chance of sunshine and minimal rain.
For those prioritizing dry weather for beach activities on the Pacific side, the months between December and April are the most reliable. Visitors traveling during the green season, from May to November, should plan their outdoor excursions for the mornings to avoid the common afternoon downpours.