Weather in Costa Rica

Costa Rica is unequivocally a tropical country, situated between 8° and 11° North latitude, fairly close to the equator. Although in the mountains above 2000 meters you get much cooler temperatures, the average annual temperature for most of the country lies between 21.7°C (71°F) and 27°C (81°F). The coolest months are from November through January, and the warmest from March through May. San José, the capital, where over a third of the population lives, stands at approximately 1170 meters altitude and has a mean annual temperature of 20.6°C (69°F).

The nation's climate is classically divided into two major seasons: rainy and dry. The dry season runs from January through May and the rainy season from May to November and December. Locally, the seasons were named by the early Spanish colonizers, who compared them to their own Mediterranean climate, calling the dry months "verano" or summer, and the rainy, grey and gloomy months "invierno" or winter. It is interesting to note that some of the coldest temperatures are registered during the early dry season or "summer". Climate is, of course, a complex phenomenon, and there are many aspects of the weather in Costa Rica that are worth examining in more detail, such as the influences of wind, rain, and topography

Weather in the tropics is essentially a phenomenon of solar radiation and air circulation. Intense heat at the equator puts air in motion, and a worldwide pattern of winds is established. The most famous of these, for Costa Rica, are the north-easterly trade winds, known locally as "alisios". These winds blow with considerable force from December to March and April. These winds, for example, are responsible for carrying moisture in the form of mists to the slopes of the Tilarán mountain range. These mists are what sustain the magnificent cloud forest ecosystem.

Rainfall patterns, although seasonal, vary greatly in intensity across geographical areas. Some locations receive over 6 mts (18 ft) of precipitation per year, while others receive under 1.5 mts (4 ft). Most of the total rainfall for any given site (about 70%) occurs on less than 15 days of a whole year, and will often be experienced as days of torrential downpour. Costa Rica may hold the world record for the amount of rainy days at one site. Hacienda Cedral registered 359 days of rain in 1968.

The topography of the country also has a great influence on the weather patterns of a given locality. As a result the timing of the dry and rainy seasons varies a bit on each slope of the mountain ranges that run from the north-west to the south-east and divide the nation into a Caribbean slope and a Pacific slope.

On the Caribbean slope the rainy season begins from mid to late April and continues through December and sometimes January. The wettest months are July and November, with a dry spell that occurs around August or September. Major storms, called "temporales del Atlantico" occasionally buffet this slope between September and February, when it will rain continuously for several days; but an average rainy season day will begin clear with a few hours of sunshine that will give way to clouds and rain by the afternoon. In contrast, the driest months of February and March, might be almost entirely without rainfall.