A major category (the A climates) in W. Köppen's 1936 climatic classification; in order to be so classified, a climate must have these two characteristics: 1) the mean temperature of the coldest month must be 18°C (64. 4°F) or higher, separating it from temperate rainy climates; 2) the annual precipitation must be in excess of a certain amount to distinguish it from dry climates (see formulas under steppe climate). The three principal types of climate included in this category are the tropical rain forest climate, tropical savanna climate, and tropical monsoon climate.