A major category (the D climates) in W. Köppen's climatic classification, defined by a coldest-month mean temperature of less than −3°C (26. 6°F) and a warmest-month mean temperature of greater than 10°C (50°F). The first limit separates it from temperate rainy climates, and the second from tundra climates. It is distinguished from the dry climates by a function of annual temperature and precipitation (see formulas under steppe climate). The outstanding feature of these climates is the cold winters with at least a month of snow-covered ground. These are the coldest of the tree climates. In C. W. Thornthwaite's classifications, this general type of climate would be 1) in the 1931 system, humid or subhumid and microthermal climate, or taiga climate; and 2) in the 1948 system, humid or moist subhumid and microthermal climate.