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Climate
There are two seasons in Costa Rica. One is a distinct dry season
from about December through March and the other a rainy season for
the rest of the year. The annual temperature averages 26.5o Celsius
(80oF) in the Diquís Valley. There is little annual variation in
temperature because of proximity to the equator. Rainfall is determined
by the presence of the Talamanca range and averages 2000-3000 mm
(78.7-118.1") per year.
Rainfall
The rainfall of the Terraba Basin is extremely variable and frequently
intense. Annual rainfall ranges from 1500 mm to 7000 mm (59"-275.5")
or more. Variation is seasonal, spatial, and elevational. The
dry season is approximately from January to April, with monthly
rainfall of 0 mm to 100 mm (0"-4"). During October,
the wettest month, rainfall may exceed 1000 mm (39"). A year
may be dry if there is influence from the weather pattern El Nino,
wet from La Nina, or otherwise considered "normal".
There are two types of rain. The first is a torrential downpour,
or aguacero, which has intense rain, thunder and lightning, but
only over a few kilometers of land. This rain has great erosive
force. The second type of rain is lighter but continuous, called
temporales. This rain often covers a larger area and often floods
low areas. In general, the effects of rain have been exacerbated
by changes in land use. Deforestation and expansion of pastures
and agriculture have increased erosion, sedimentation, and potential
for flooding. Hurricanes are another disturbance that usually
bring heavy rain and flooding.
Due to the
heat and humidity of the Diquís Valley, few activities take place
mid-day.
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