The Köppen code for a tropical rainforest climate is Af. The first letter, A, identifies a tropical climate, while f means there is no dry season under the classification’s rainfall criteria.
An Af climate has average temperatures of at least 18°C in every month and receives at least 60 millimetres of precipitation in each month. These conditions produce year-round warmth and persistent moisture, supporting dense evergreen forests in many equatorial regions.
Tropical rainforest climates are common near the Equator, often within roughly 10° latitude, where the Intertropical Convergence Zone brings frequent rising air, clouds, and rainfall. However, some higher-latitude coastal locations also qualify because of maritime moisture and warm ocean currents.
The main mix-up is with Am, the tropical monsoon climate, and Aw, the tropical savanna climate. Both can be hot year-round, but they have a defined drier month or dry season; Af does not.