In general, the climate of the ice cap regions of the world; thus, it requires temperatures sufficiently cold so that the annual accumulation of snow and ice is never exceeded by ablation. The perpetual frost climate is one of the polar climates in W. Köppen's climatic classification and is characterized by a warmest-month mean temperature of less than 0°C (32°F). It is designated by letter code EF and is equivalent to the frost climate of C. W. Thornthwaite's classifications and to Nordenskjöld's (1928) high arctic climate.