The rain is constant, in the form of torrential downpours, showers and drizzles, which bring from 2,700 mm,. in the lowlands to 7,555 mm. in the intermediate area at around 2,000 meters above sea level.  The river rushes headlong down the steep slopes, feeding a vast network of waterways that belong to the River Grande de Orosi and are used to generate hydroelectric energy.

In such a steep and rainy natural environment, the trees do not need to put down deep roots to get water.  As a result, they are easy victims of landslides and tremors, which are frequent in this river basin.  The avalanches of mud and rocks have swept away bridges and roads downstream in the Reventazón River Valley.  If trees do not have deep roots, they cannot support thick branches and large crowns and therefore these forests are only of medium height.  On the other hand, they house a wealth of epiphytes, palms, bamboo stands, and tree ferns.  A cloud forest, thick with mosses and bromeliads, grows above 1,500 meters.