Climate
The Köppen classification depends on average monthly values of temperature and precipitation. The most commonly used form of the Köppen classification has five primary types labeled A through E. These primary types are A) tropical, B) dry, C) mild mid-latitude, D) cold mid-latitude, and E) polar. The five primary classifications can be further divided into secondary classifications such as rainforest, monsoon, tropical savanna, humid subtropical, humid continental, oceanic climate, Mediterranean climate, desert, steppe, subarctic climate, tundra, and polar ice cap.
Trewartha climate classification
Trewartha's modifications to the 1899 Köppen climate system sought to reclass the middle latitudes into three groups: "C" (subtropical)—8 or more months have a mean temperature of or higher; "D" temperate—4 to 7 months have a mean temperature of 10 °C or higher; and "E" boreal climate—1 to 3 months have a mean temperature of 10 °C or higher. Otherwise, the tropical climates and polar climates remained the same as the original Köppen climate classification.