Climatology
This page presents Costa Rica's climate context for the current climatology, 1991-2020, derived from observed, historical data. Information should be used to build a strong understanding of current climate conditions in order to appreciate future climate scenarios and projected change. You can visualize data for the current climatology through spatial variation, the seasonal cycle, or as a time series. Analysis is available for both annual and seasonal data. Data presentation defaults to national-scale aggregation, however sub-national data aggregations can be accessed by clicking within a country, on a sub-national unit. Other historical climatologies can be selected from the Time Period dropdown list.
Observed, historical data is produced by the Climatic Research Unit (CRU) of University of East Anglia. Data is presented at a 0.5º x 0.5º (50km x 50km) resolution.
Costa Rica’s climate is characterized by well-defined annual patterns. However, these are periodically affected by fluctuations in the temperature of the surrounding oceans, interaction of the atmospheric circulation with the volcanic mountain range that runs northeast to southeast, and the El Niño/La Niña cycles as well as Pacific Decadal Oscillation (PDO). Regional long-term variabilities are also influenced by annual north-south displacement of the Intertropical Convergence Zone (ITCZ), the intensity of the subtropical high-pressure system over the Caribbean Sea, the strength of the trade winds and of the Caribbean Low-Level Jet (CLLJ).
Costa Rica’s mountains, dominant wind patterns and ocean influences characterize the seven recognized climatic zones of Costa Rica: North Pacific, Central Pacific, South Pacific, Central, North, and Caribbean North and Caribbean South. The lowland regions of the country harbor a tropical and subtropical climate, while the highlands experience colder climates. The El Niño phenomenon causes severe droughts on the Pacific coast of Costa Rica, while masses of cold air moving in from North America during the winter months combine with the trade winds between July and August to produce intense rains that cause flooding on central Costa Rica’s Caribbean slope. The interactions between the trade winds from the east and the region’s topographic diversity creates the effects of “rain shadow,” with the Caribbean slope experiencing rain practically all year round. The Pacific slope is characterized by a prolonged dry season lasting approximately from November until April or May and a wet season during the rest of the year. The increased intensity of the trade winds in July produces a peak of precipitation on the Caribbean slope. Daily temperatures reach their maximum value before the start of the rainy season. Minimum temperatures show a different pattern, with the highest values observed in July and the lowest values during the Northern Hemisphere winter.
In recent decades, Costa Rica has seen significant changes in the patterns of precipitation and increases in temperatures, as well as in land use and its degradation. Variability continues to mark the annual expression of climate, since the frequency and intensity of multiple phenomena can increase or decrease. Therefore, the climate of Costa Rica, in its different regions, will be marked by dry extremes, such as the drought of 2008 and rainy extremes, such as during the El Niño of 2014-2015. Costa Rica has already experienced the negative impacts of climate variability, including by record economic losses from extreme hydrometeorological events, including such as episodes of the El Niño Southern Oscillation (ENSO).