True tropical rainforests are diverse ecosystems distributed around the equator with high rates of precipitation. The trees found in a tropical rainforest are primarily broad-leaved species that form a dense canopy of foliage above the forest floor that acts as a wind buffer and decreases wind speeds below the canopy. Even above the canopy most tropical rainforests experience minimal winds, a factor that contributes to the overall hot and humid climate.
The temperature in a tropical rainforest rarely dips below 18 degrees Celsius (64 degrees Fahrenheit), and annual precipitation is between 70 and 100 inches. Atmospheric humidity hovers near 100 percent for days at a time, and with typically heavy cloud cover, it is standard for a tropical rainforest to receive only five or six hours of sunlight in a day. Wind speed can increase slightly with increased elevation in a rainforest, and temperature falls by about one-half of a degree for every 100-meter gain in altitude.
Tropical rainforests experience very light winds that make the climate feel even more humid and warm. The average wind speed above the canopy of a tropical rainforest is 10 kilometers (6.2 miles) per hour, and very often winds will stay below 5 kilometers (3 miles) per hour. Maximum wind speeds are recorded at higher elevations on rainforest slopes, with maximum speeds in the canopy of the Monteverde tropical cloud forest easily reaching 64 kilometers (40 miles) per hour or more.
Below the Canopy
Wind speeds are even slower when measured below the forest canopy. Because tropical rainforests consist of large stands of broad-leaved trees, any breeze passing above the dense canopy is hampered in the understory. One study in the "Journal of Applied Meteorology" found wind speeds near the forest floor in a Colombian jungle were typically between 1 and 5 percent of the speed recorded above the canopy.
The wind speed in a tropical rainforest fluctuates depending on the time of year, and even the time of day. Most tropical rainforests have a dry season of several months where rainfall decreases and wind speeds experience a slight uptick. On a day-to-day basis the wind in a rainforest peaks around noon and is slowest in the early morning.