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
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
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 )
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
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.
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.)