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.