The Köppen climate classification code for a tropical rainforest climate is Af.
The first letter A identifies a tropical climate, meaning every month has an average temperature of at least 18°C. The lowercase f means there is no dry season: precipitation remains sufficiently high throughout the year. Together, Af describes climates that are hot and humid with abundant year-round rainfall.
Af climates occur in parts of the Amazon Basin, the Congo Basin, Indonesia, and other regions near the equator. They support dense evergreen forests, although actual vegetation also depends on soil, elevation, drainage, and human land use.
The code is often confused with Am and Aw. Am denotes a tropical monsoon climate with a short dry period, while Aw denotes a tropical savanna climate with a pronounced dry winter or dry season. Köppen codes describe long-term climate averages, not the weather on a particular day or the exact boundaries of every rainforest.