Regions having a subarctic climate (also called boreal climate) are characterized by long, usually very cold winters, and brief, warm summers. It is found on large landmasses, away from the moderating effects of an ocean, generally at latitudes from 50° to 70°N. Due to the absence of any large landmasses at such latitudes, it is not found in the Southern Hemisphere. These climates represent Köppen climate classification Dfc, Dwc, Dfd and Dwd.
This type of climate offers some of the most extreme seasonal temperature variations found on the planet: In winter, temperatures can drop to -40°C (also -40°F) and in summer, the temperature may exceed 30°C (86°F). However, the summers are short; no more than three months of the year (but at least one month) and must have a 24-hour average temperature of at least 10°C (50°F) to fall into this category of climate. The subarctic climate is a subset of the continental climate. The subarctic climate is found in the following areas:
- Much of Siberia
- The northern half of Scandinavia (milder winters in coastal areas)
- Most of Alaska
- Much of Canada from about 50°N to the tree line, including:
With 5-7 consecutive months where the average temperature is below freezing, all moisture in the soil and subsoil freezes solidly to depths of many feet. Summer warmth is insufficient to thaw more than a few surface feet, so permafrost prevails under large areas. Seasonal thaw penetrates from 2 to 14 ft (0.6 to 4 m), depending on latitude, aspect, and type of ground. Some northern areas with subarctic climates near oceans (southern Alaska and the northern fringe of Europe), have milder winters and no permafrost, and are thus more suited for farming.
The frost-free season is very short, varying from about 45 to 100 days at most, and a freeze can occur during any month in many areas. Vegetation in a subarctic climate is generally of low diversity, because only hardy species can survive the long winters and make use of the short summers. Trees are mostly limited to ferns and evergreen conifers, as few broadleaved trees are able to survive the very low temperatures in winter. This type of forest is also known as taiga, a term which is sometimes applied to the climate found therein as well. Even though the diversity may be low, numbers are high, and the taiga (boreal) forest is the largest forest biome on the planet, with most of the forests in Russia and Canada.
Agricultural potential is generally poor, due to the natural infertility of soils and because of the many swamps and lakes left by departing ice sheets, and short growing seasons allow only the hardiest of crops. (Despite the short season, the long summer days at such latitudes do permit some agriculture.)
There is very little precipitation, no more than 15 to 20 inches over an entire year and, away from the coasts, occurs mostly in the warmer months. Low precipitation, by the standards of more temperate regions with longer and warmer winters, is typically sufficient in view of the very low evapotranspiration to allow a water-sogged terrain in many areas of subarctic climate.
Poleward or even approaching polar seas, the warmest month has an average temperature of less than 10°C (50°F), and the subarctic climate grades into a tundra climate even less suitable for trees.
Sample locations with such climates:
- Fairbanks, Alaska
- Whitehorse, Yukon
- Yellowknife, Northwest Territories
- Thompson, Manitoba
- Moosonee, Ontario
- Goose Bay, Newfoundland and Labrador
- Rovaniemi, Finland
- Kiruna, Sweden
- Arkhangelsk, Russia
- Irkutsk, Russia
- Chita, Russia
Sample locations with the extreme Dfd climate include: