The polar climate (also called subartic, or boreal) is characterized by long very cold winters and short cool summers. Only found on large landmasses. This climate offers the most extreme seasonal temperature variations (70o swing between the average summer and winter).
With over at least half of the months averaging below freezing, all moisture in the soil and subsoil freezes solid. Summer is insufficient to thaw more than a few meters (0-4 meters) of the surface (permafrost). Very little precipitation away from the coasts, except at high altitudes.