Humid continental climate

A humid continental climate (Köppen prefix D and a third letter of a or b) is a climatic region defined by Russo-German climatologist Wladimir Köppen in 1900, typified by large seasonal temperature differences, with warm to hot (and often humid) summers and cold (sometimes severely cold in the northern areas) winters. Precipitation is usually distributed throughout the year. The definition of this climate regarding temperature is as follows: the mean temperature of the coldest month must be below −3 °C (26.6 °F) (or 0 °C (32.0 °F)) and there must be at least four months whose mean temperatures are at or above 10 °C (50 °F). In addition, the location in question must not be semi-arid or arid. The Dfb, Dwb and Dsb subtypes are also known as hemiboreal. A humid continental climate (Köppen prefix D and a third letter of a or b) is a climatic region defined by Russo-German climatologist Wladimir Köppen in 1900, typified by large seasonal temperature differences, with warm to hot (and often humid) summers and cold (sometimes severely cold in the northern areas) winters. Precipitation is usually distributed throughout the year. The definition of this climate regarding temperature is as follows: the mean temperature of the coldest month must be below −3 °C (26.6 °F) (or 0 °C (32.0 °F)) and there must be at least four months whose mean temperatures are at or above 10 °C (50 °F). In addition, the location in question must not be semi-arid or arid. The Dfb, Dwb and Dsb subtypes are also known as hemiboreal. Humid continental climates are generally found roughly between latitudes 40° N and 60° N, within the central and northeastern portions of North America, Europe, and Asia. They are much less commonly found in the Southern Hemisphere due to the larger ocean area at that latitude and the consequent greater maritime moderation. In the Northern Hemisphere some of the humid continental climates, typically in Scandinavia, Nova Scotia, and Newfoundland are heavily maritime-influenced, with relatively cool summers and winters being just below the freezing mark. More extreme humid continental climates found in northeast China, southern Siberia, the Canadian Prairies, and the Great Lakes region of the American Midwest and Central Canada combine hotter summer maxima and colder winters than the marine-based variety. Using the Köppen climate classification, a climate is classified as humid continental when the temperature of the coldest month is below −3 °C (or 0 °C ) and there must be at least four months whose mean temperatures are at or above 10 °C (50 °F).These temperatures were not arbitrary. In Europe, the −3 °C average temperature isotherm (line of equal temperature) was near the southern extent of winter snowpack. The 10 °C average temperature was found to be the minimum temperature necessary for tree growth. Wide temperature ranges are common within this climate zone. Second letter in the classification symbol defines seasonal rainfall as follows: while the third letter denotes the extent of summer heat: Within North America, moisture within this climate regime is supplied by the Gulf of Mexico and adjacent western subtropical Atlantic. Precipitation is relatively well distributed year-round in many areas with this climate (f), while others may see a marked reduction in wintry precipitation, which increases the chances of a wintertime drought (w). Snowfall occurs in all areas with a humid continental climate and in many such places is more common than rain during the height of winter. In places with sufficient wintertime precipitation, the snow cover is often deep. Most summer rainfall occurs during thunderstorms, and in North America and Asia an occasionally tropical system. Though humidity levels are often high in locations with humid continental climates, the 'humid' designation means that the climate is not dry enough to be classified as semi-arid or arid. By definition, forests thrive within this climate. Biomes within this climate regime include temperate woodlands, temperate grasslands, temperate deciduous, temperate evergreen forests, and coniferous forests. Within wetter areas, maple, spruce, pine, fir, and oak can be found. Fall foliage is noted during the autumn. A hot summer version of a continental climate features an average temperature of at least 22 °C (71.6 °F) in its warmest month. Since these regimes are limited to the Northern Hemisphere, the warmest month is usually July or August. For example, Chicago has average July afternoon temperatures near 29 °C (84 °F), while average January afternoon temperature are near −1 °C (30.2 °F). Frost free periods normally last 4–7 months within this climate regime. Within North America, this climate includes small areas of central and southeast Canada (including the City of Toronto, which is otherwise surrounded by the warm-summer type), and portions of the central and eastern United States from the 100th meridian eastward to the Atlantic. Precipitation increases further eastward in this zone and is less seasonally uniform in the west. The western states of the central United States (namely Montana, Wyoming, parts of southern Idaho, most of Lincoln County in Eastern Washington, parts of Colorado, parts of Utah, western Nebraska, and parts of western North and South Dakota) have thermal regimes which fit the Dfa climate type, but are quite dry, and are generally grouped with the steppe (BSk) climates.