Costa Rica Weather
Costa Rica is a tropical country in every sense of the word and with an average annual temperature for most of the country that lies between 21.7°C (71°F) and 27°C (81°F). Of course if you climb into the mountains above 6,500 feet (2,000 meters) the temperatures are noticeably cooler especially at night.
This paradise for birds offers a climate that is divided into 2 main seasons, the dry season that extends from mid December through the end of April and the rainy season that falls from May to mid December.
The most influential weather flow comes about due to the north-easterly trade winds. The strength of these winds is at its peak from December to April and can blow with considerable force.
Province By Province Weather Breakdown
This province is comprised of the small western tip of the Central Valley that is known for its warm sunny climate but most of the Alajuela Province lies north and west of the countries northern volcanic mountain ranges and covers a territory that runs to the Nicaraguan border. This expansive region in the northern lowlands is influenced by the climatic conditions that blow in from the Caribbean Sea. This brings significant rains to this area and an even wetter and cooler climate as these volcanic mountains slope off to the Caribbean.
This province encompasses an area that includes the Reventazon River valley and the adjacent towering mountains to the north that are home to both the Irazu and Turrialba Volcanoes. To the south this region is home to Cerro de la Muerte and Mount Chirripo. The trade winds blow moisture over most of this area with only the city of Cartago protected from the rains by the rain shadow created by the Irazu volcano The area immediately around Cartago is one of the driest areas in Costa Rica. For the most part Cartago province is located in an area of high elevation and gathers more clouds and cooler temperatures than other parts of the country.
The climate all over this province is hot with distinct wet and dry seasons. The portions of the province that cover the highlands of the upper Pacific-facing slopes of the volcanic mountain ranges of Guanacaste and Tilaran have a climate that is cool and moist that provides the needed moisture to sustain verdant cloud forests. The rest of the province is covered with tropical dry forest.
If dry and hot are what you like then you will find it here. This area will experience up to 6 months of very dry weather. Once the trade winds shift to bring Pacific moisture on shore the arid countryside quickly recuperates and the brown countryside explodes into a verdant display of tropical plant life.
Heredia province covers a segment of the Central Valley and the Central Volcanic Mountain range with the largest portion of its territory located in the northern lowlands, south of Nicaragua. This province has a wide range of climatic conditions from the balmy and moist lowlands, to fresh and damp highlands, to the placid but seasonally wet and dry Central Valley.
This province includes both low lying coastal lands as well as mountainous territory. The weather here is under the direct influence of the northeast trade winds and the warm moist air they carry into this region. Here you will find no clearly defined dry season, with a decrease in the rains during March, April, September and October. The heaviest rains fall here during June, July, August, November and December.
Puntarenas province offers examples of all climate types. The northeast trade winds that come in off the Caribbean Sea are for the most part stripped of their water and power by their climb over the mountains of the Central Volcanic mountain range before they can dump their moisture on the Pacific side of those mountains. The movement of weather systems over these mountains creates a turbulence that forms a vortex and reverses the air flow which usually brings very dry weather and essentially draws weather systems from the Pacific Ocean that produce scattered precipitation in the dry season. These intermittent rains and related elevated humidity help maintain the lush jungle of this southern coastal area. The driest period here runs from January through April.
The central parts of the province, that climb to the mountain tops, are covered with abundant cloud forests that survive because of the mists that do make it across this volcanic chain of mountains pushed by the trade winds. This moisture arrives December through February.
San Jose province also includes areas under the influence of virtually every feasible weather pattern in Costa Rica. This province runs from near sea level to the highest point in the country, Mt. Chirripo. A little part of this territory runs down the very wet Caribbean slopes of the Central Volcanic mountain range that is part of Braulio Carrillo national park
The greater part of this territory has a moderate weather system offering a climate that requires little protection from cool evenings. This placid weather region is located at an altitude between 2,300 and 4,300 feet above sea level. Here you will find a dry season that runs from the middle of November through the middle May. The rainy season shows up during the rest of the year.