CLIMATE IN COSTA RICA
Due to the fact that Costa Rica is located between 8 and 12 degrees north of the Equator, we do not suffer the drastic changes of temperatures between one seasonal period and another, that characterize the temperate and cold zones. The major part of the Costa Rican territory enjoys thermal stability throughout the year. In some zones of Guanacaste, the increase in temperature is associated with the dry season and the large amount of daylight hours with clear skies.
The parameter that does produce temperature changes is the altitude, and because Costa Rica is a country with great altitudinal variations ( from sea level to more than 3800 meters ), this effect is considered of great importance. In the highlands the temperatures are low during the whole year. At high elevations the temperature can drop many degrees during the coldest hours of the night, ( in the highest points the temperature can go below 0 C ) but increase with the sunlight during the daylight.
At the other extreme to this situation are the lowlands, where temperatures do not descend less than 20 C and not higher than 30 C. In the major part of the Central Valley, the maximum temperature ( around 28 C ) is reached a little after midday and descends gradually to about 20 C around 7:00 p.m. It stays stable during the night and reaches the minimum ( around 18 C ) around 4:00 a.m., it overcomes the 20 C point at 7:00 a.m. and increases gradually to midday.
This pattern of daily oscillation is constant during the whole year, although, naturally, during the rainy season the temperatures tend to be lower and descend faster during the afternoon. The hibernation fronts in december and january make the temperature descend considerably.
It has been talked of in recent years about global warming of our planet. The intense industrial outpourings and the growing world population are in part responsible for some of these changes. The fact is that a general change in the planets´s temperature would implicate a change in distribution patterns of rainfall, in the sea level and other climatic factors all over the world..
Because Costa Rica is located in the northern hemisphere, the dominant winds of its climate are the north easterly trade winds.
The Northern Winds
The northern winds are cold and dry winds that blow in our national territory in December and January. Because of the cold weather in the North American continent during this time of the year, the zone of high pressure intensifies to a latitude approx. 30 degrees North and these winds descend to the south reaching our territory. These cold and dry winds penetrate until the Central Valley in Costa Rica, producing the typical climate of the end of the year.
In Costa Rica there are no real dry zones, because the minimum rainfall is of 1200 mm per year ( 48 inches ). On the other hand, there are zones with 8000 mm ( 320 inches ) of rainfall per year.
In general terms, in Costa Rica we can talk about 2 rainfall regimes:
The Pacific ( often called tropical ), characterised by a very well defined dry season, and the Caribbean ( many times called equatorial ) , with the permanent influence of the north easterly trade winds and without a dry season.
In the Caribbean regime, there are 2 very different systems. On one side, the coast lowlands and northern plains, that present a notable decrease of rainfall during March and April and sometimes September, and on the other side, the mountains and slopes exposed to the trade winds, where it rains all year long without appreciable interruption.
CLIMATE AND CLOTHING
Costa Rica is located 10 degrees north of the Equator, and has no seasons as found in the temperate zones. The temperatures are the same all year long with small variations. In the Central Valley, where the capital city San Jose is located, the temperature average is 21 degrees centigrade ( 74 Fahrenheit ). On the coast the temperatures vary from 24 to 30 degrees. During the months of December, January and February the temperature may decrease 3 or 5 degrees centigrade due to a north breeze.
The next items are recommended for your trip :
Sweater or jacket for cool weather, depending on the places to visit
Tennis shoes or hiking boots
At least a pair of slacks or pants
Camera and enough film ( film is more expensive in Costa Rica )
CLIMATE THE CARIBBEAN REGION
This region, that encompasses the Caribbean and Northern slopes, present temperatures according to the altitude. The whole region is directly exposed to the north easterly trade winds, which are fully loaded with the humidity of the Caribbean Ocean. Part of this humidity precipitates in the coasts and plains, but the major rainfall occurs in the slopes of the range of mountains due to the topographic effect.
This kind of rainfall is due to the winds, that are being forced to climb because of the mountains, they lose temperature slowly and create the condensation and the subsequent rainfall.
This rainfall regime will decrease during 2 periods of the year, March-April and August-September, because of modifications produced in the tradewinds by the relative position of the sun. Nevertheless, in these zones there is no defined dry season.
The highest rainfall occurs in the mountains, particularly between 1000 and 2000 meters ( 3000 and 6000 feet ) of altitude, with major precipitations of 5000 mm ( 200 inches ). The highest amounts of rainfall have been registered in the cuenca of the Reventazon River, where 8000 mm ( 320 inches ) fall yearly, and more at other sites. At altitudes higher than 2000 m ( 6000 feet ) the rainfall tends to decrease
Storms in the Atlantic
They correspond to a variable period ( up to 15 days ) in which rain and drizzle predominate that could last all day and night. They occur mainly during the winter and in the north.
CLIMATE THE PACIFIC REGION
The fundamental characteristic of the climate of the Pacific is the presence of a dry season that lasts for 4 months and more in some zones. Also there is an important characteristic, a short dry period during half of the year, known as veranillos ( little summers )
During this period, the Pacific region is inside the convergence zone, where the winds from the west strengths those already existing and produce the rainy season with all its intensity. This period extends from mid May to the end of November, and it is only interrupted by the veranillos. ( little summers ). The veranillos last for a period of one to two weeks , almost always in July, where precipitation decreases considerably in all the Pacific Zone. When it occurs early ( end of June ), its known popularly as ” Veranillo de San Juan “, if it occurs in July or beginning of August, sometimes with alternatives of dry and rainy days, the countryside men know it as caniculas. This phenomena, is due, basically to the changes of the zenithal position of the sun.
Rainfall in the Osa Peninsula
The region of the South Pacific receives considerably more rainfall than Guanacaste and the north of Puntarenas, and so much more than many localities of the Caribbean. Nevertheless, different than the Caribbean, this region has a period with a defined decrease of rainfall.
Storms in the Pacific
During the summer in the north ( from July to end of November ), frequently, zones of low pressure are formed in the Caribbean region, where winds are produced that rotate in opposition to clockwise to the centre of the depression. This produces strong winds and rain in the Pacific Region that sometimes may turn into hurricanes. Costa Rica is far away from the preferential route of hurricanes, this is why we mainly get their indirect effects – to the Pacific Littoral. ( With the exceptions of Joan in 1983 and Mitch in 1998, that dangerously approached our Caribbean coast, causing devastating flooding results.)