In geography, the region between the Tropics of Cancer and Capricorn is called the tropics. Costa Rica is located in this region, which gives its ecological surroundings – its forests, waters, soils and climate – certain tropical characteristics. Its flora and fauna are adapted to these conditions, meaning that they are tropical as well.
This tropical climate is modified by various factors, including relief (mountains, plains and plateaus), its position on the Central American isthmus, the influence of the oceans (winds and sea breezes and the temperature of ocean currents) and the general atmospheric circulation. The interaction of all of these local geographic, atmospheric and oceanic factors are the main causes of the country’s regional climate.
The northwest-southeast orientation of the mountain range divides Costa Rica into two sides: the Pacific and the Caribbean. Each one of these has its own precipitation and temperature regimen with particular spatial and temporal distribution.
The Pacific region is characterized by a well-defined dry and rainy season.The dry season lasts from December to March. April is a transition month. The driest and hottest month is March.The Pacific region begins in the northwest and ends in the southeast, meaning that the dividing line changes from north to south.
The rainy season goes from May to October, with November being a month of transition.There is a relative decrease in the amount of rain during the months of July and August, which are termed veranillo, or “little summer”.These months are marked by an intensification of the trade winds.The rainiest month are September and October, mainly due to the influence of the cyclone systems, the monsoon winds from the equatorial Pacific Ocean, and the sea breezes.
The rains mainly occur during the afternoon and early evening.
The climate regime of this side of the country does not have a well-defined dry season, since the rains remain steady between 100 and 200 mm in the driest months, which is a considerable amount.
Two relatively dry periods exist in the coastal zones. The first dry period is between February and March and the second between September and October.
The first dry period is in sync with the Pacific dry season, while the second period occurs during the rainiest months on the west coast.In addition, there are two rainy periods between the dry ones. The first one goes from November to January and is the strongest rainy period.
The second one stretches from May to August and is characterized by a maximum in July that coincides with the “little summer” in the Pacific.The rainiest month is December, which is influenced by the effects of cold fronts coming from the Northern Hemisphere, which are present between November and May, though their greatest effect is felt between November and March. Rain falls mostly during the night and morning.
The two precipitation regimes mentioned above, along with the height and orientation of the mountains and the prevailing winds and the influence of the oceans, allow the identification of seven main climatic regions in Costa Rica.
This region is located in the northwest of the country, including Guanacaste, the Puntarenas cantons of Esparza and Montes de Oro and those of Orotina and San Mateo in Alajuela.
It is an extensive, coastal region with tropical forests, dry forests and wetlands.
The region is characterized by the continental mass made up of the Cordillera de Guanacaste and Cordillera de Tilarán mountain ranges (with an average altitude of 1,000 meters above sea level, or masl), the peninsulas of Nicoya and Santa Elena (300 masl) and the Tempisque depression (30 masl).
The dry period lasts from December to March, with 4% of annual precipitation falling in these months. April is a transition month, with the rains setting in from May to August (50% of annual precipitation).
June is the first peak month of rain, while the Pacific veranillo comes in during July and August with the intensification of the trade winds. The second rainy period lasts from September to November, giving way to the transition into the dry season.
Located in the central region of the Pacific side of Costa Rica, it extends from Playa Herradura or Jacó to Dominical, following the ridge formed by Cerro Herradura, Cerro Turrubares, Cerro Cangreja and the lower coastal mountains. It contains the towns of Tinamaste, Valle de Parrita, Quepos and Manuel Antonio.
It has timber harvesting regions as well as watershed and wildlife protection areas.
The physiographic region made up of the Osa Peninsula and the coastal region of the Pacific from Puntarenas to Golfo Dulce. It is divided into the Candelaria and Parrita Valleys, which are divided by a secondary mountain chain. Precipitation is higher in the valleys and in the south of the region, with an average annual precipitation of 3,500 mm.
The climate is tropical, with a short and moderate dry season, but it has a very intense and long rainy season towards the south.
The maximum average temperature is 31°C (89°F), while the average minimum temperature is 22.7°C (73°F). The dry season lasts from January to March. April is a month of transition, which precedes the rains that arrive at the beginning of May and last into August. December is a transition month.
It is located to the southeast of the Central Pacific region, extending form Punta Uvita to San Isidro del General. It includes the Panama border region, extending to Punta Burica. The region encompasses the Valle del General, the Peninsula de Osa, Golfito and the valleys of Coto Colorado and Coto Brus.
It is a peninsular plain with areas of tropical rainforest with high biodiversity, making Corcovado National Park one of the richest areas in Latin America.
It has two physiographical regions: the Cordillera de Talamanca, which is subdivided into the Coastal Ridge and the Lower Tectonic Region (which includes the Valle del General, Coto Brus and Punta Burica), and the Osa Peninsula. The total precipitation increases towards the south.
Less rain falls in the higher parts of the cordillera (2,500-3,000 mm).
Its average maximum temperature is 27.9°C (82°F), while the minimum is 20.5°C (68.9°F). The dry season lasts from January to March, with April as a transition month.
Valle del General is an exception, as the rains there begin at the end of April and beginning of May. The first rainy season is between May and August.
This region is located in the country’s center and is bordered to the north by the Central Volcanic Range, the Cerros de Escazú, Tablazo, Cedral and the Candelaria Ridge to the south, the Monte del Aguacate to the west and the Cordillera de Talamanca to the east. It includes the country’s largest urban centers: San José, Heredia, Alajuela and Cartago.
According to the Holdridge life zone classification, it contains areas ranging from wet tropical forest to rainy premontane forests. Some areas contain wet tropical forests with average temperatures of 22°C (72°F) and annual precipitation of 2,300 mm on average.
This region is part of the Volcanic Structural Region and the Tilarán Band, which holds valleys that are influenced by the conditions of the Pacific and the Caribbean.
- Western Central Valley: Its lower regions (Atenas, Turrúcares, La Garita and La Guácima) have a dry climate with a marked influence from the Pacific. Its intermediate regions (San José, Heredia, Cartago) experience a temperate climate, while the higher regions are rainy and cold, typical of the mountainous area. It has around 148 rainy days.
- Eastern Valley: This includes the valleys of El Guarco and Orosi, with weaker rain that comes over the mountain passes and is mostly influenced by the Caribbean weather system. It has around 163 rainy days, mostly in the months of December, January and February.
However, the Western Valley has higher total precipitation (2,300 mm) than the Eastern Valley (1,700 mm).
In general, the Central Region has a dry season that lasts between December and March and a rainy period between May and October. A very popular veranillo occurs at the end of June, known as the “Veranillo de San Juan”.
Temperature varies with altitude, with lower temperatures at higher locations.
The Western Valley has an average altitude of 1,100 masl, while the Eastern Valley is higher, at 1,300 masl. The highest temperatures are observed in March and April in the former, and in April and May in the latter.
This region is located in the north of Costa Rica, bordering on the Río San Juan and Nicaragua in the north, the Central Volcanic Range in the south, and the Cordillera de Guanacaste and Cordillera Tilarán in the west. The Río Chirripó is generally taken to be the eastern border between this region and the Caribbean.
It has wet tropical forest regions with a transition to a dry forest.
It belongs to the Caribbean precipitation region, which is rainy year-round, with a relative decrease in February, March and April. It is a region with contrasting rainfall, since climatic elements and geographical factors interact due to its mountainous relief and the presence of extensive plains, in addition to the presence of Lake Nicaragua to the northwest.
This region is the third-wettest in the country, with over 3,200 mm per year on average, surpassed only by the Southern Pacific and the Northern Caribbean.
Its rainy season begins in May and ends in December/January.
Situated in the country’s east and northeast, it extends over the entire Caribbean coast from Barra del Colorado to the Río Sixaola. It is bordered to the south by the Cordillera de Talamanca and to the west by the Río Chirripó. It is made up of the province of Limón and the eastern part of Cartago - the eastern part of the Turrialba Canton.
The northern part of the region encompasses Barra del Colorado, the Tortuguero plains and the Talamanca foothills.
The Mirador and Asunción ridges south of Siquirres form one border, while its southern extent is limited by the city of Limón.
The southern region consists of Turrialba, part of the Cordillera de Talamanca, the Valle de la Estrella and Sixaola, extending to the Caribbean coast.
This region is characterized by wet tropical forest that with rich, lush vegetation. Its plains are used to cultivate banana, root crops and staple grains.
The coastal plains of the north (Tortuguero, Santa Clara and Matina) have heavier rainfall than the southern plains of Estrella and Sixaola.
The monthly and annual precipitation records suggest a difference between the northern and southern regions. The annual precipitation gradient decreases from north to south, with the north receiving 3,500-4,500 mm annually and the south receiving 2,500-3,000.
Both the maximum and minimum temperatures tend to be somewhat higher in the northern sub-region.
There are two rainy seasons in both regions: the first, between September and October and the second from February to March.
It is important to mention that the following climatic categories can be distinguished in the country:
- The páramo: altitudes of 3,000-3,100 m or higher, with temperatures that fall to 0°C (32°F).
- Warm temperate: altitudes above 1,500 m, with average temperatures from 14-18°C (57-64°F).
- Wet temperate: altitudes under 1,100 m, with average temperatures from 25-26°C (77-79°F).
- Tropical: regions with a pronounced dry season and temperatures between 26-27°C (79-80°F).
- Intermontane valleys with altitudes of between 1,000 and 1,100 m, characteristic of the Central Valley, with temperatures that range between 14-18°C (57-64°F).
For more information on Costa Rica’s climatological conditions, please check the website of the Meteorological Institute of Costa Rica at www.imn.ac.cr , which was our source of information for this note.