Cartographically speaking, the subpolar regions include all parts of the world just outside the Arctic and Antarctic Circles. However, the climates considered truly subpolar are found only in the northern hemisphere. The southern hemisphere contains very little land in these latitudes, and what lands do exist benefit greatly from the oceans' moderating effects.
Under the Köppen-Tregartha system, the type of climate found in the subarctic is designated D. Often called boreal forest climates -- "boreal" means "northern" -- their seasonal fluctuations tend to be extreme and winter precipitation usually falls as snow. They are further distinguished by adding single lower-case letters, describing typical precipitation. There are two subcategories: f indicates a location that is wet year-round and w describes a region with a dry winter and a wet summer.
By Dave Bryant, copyright 2002