In W. Köppen's 1936 climatic classification, any type of climate that supports the growth of trees. This includes the tropical rainy climates, temperate rainy climates, and snow- forest climates. Excluded are the dry climates and polar climates.
Tree climates are separated from polar climates by the isotherm representing the warmest month mean temperature of 10°C (50°F). They are separated from the dry climates by a certain value of annual precipitation as a function of temperature. In this latter sense they are also known as rainy climates.
See Köppen–Supan line, arctic tree line.
Köppen, W. P., and R. Geiger 1930–1939. Handbuch der Klimatologie. Berlin: Gebruder Borntraeger, 6 vols.
