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How do clouds and humidity affect the climate of tropical rainforests?

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Ecuador: rainforest — Tropical rainforest Rainforest vegetation grows along the northern coast of Ecuador.

In tropical rainforests, clouds and humidity are fundamental to maintaining the region's hot, wet climate.1

The Role of Cloud Cover

High levels of cloud cover act as a natural regulator of solar radiation, limiting daily sunshine hours to between four and six. By blocking incoming sunlight, clouds prevent temperatures from reaching the extreme highs often recorded in drier tropical regions. In mountainous areas, moisture-laden air currents forced upward by topography cool and condense, creating persistent cloud forests where a layer of clouds at the canopy level is common year-round.12

The Impact of Humidity

Atmospheric humidity in these regions is consistently high, typically exceeding 50 percent during the day and approaching 100 percent at night. This moisture contributes to the "discomfort" of the climate, as high humidity combined with light winds limits cooling. Within the forest structure, the dense vegetation further increases humidity and reduces wind speeds relative to the area above the canopy. Furthermore, this moisture is essential for epiphytes, which derive water and nutrients directly from the air.12