Humid continental climate
A humid continental climate is a climatic region defined by Russo-German climatologist Wladimir Köppen in 1900, typified by four distinct seasons and large seasonal temperature differences, with warm to hot (and often humid) summers and freezing cold (sometimes severely cold in the northern areas) winters. Precipitation is usually distributed throughout the year but often do have dry seasons. The definition of this climate regarding temperature is as follows: the mean temperature of the coldest month must be below or depending on the isotherm, and there must be at least four months whose mean temperatures are at  or above . In addition, the location in question must not be semi-arid or arid. The cooler "Dfb", "Dwb", and "Dsb" subtypes are also known as hemiboreal climates. Humid continental climates are generally found between latitudes 30° N and 60° N, within the central and northeastern portions of North America, Europe, and Asia. They are rare and isolated in the Southern Hemisphere, due to the larger ocean area at that latitude, smaller land mass, and the consequent greater maritime moderation. In the Northern Hemisphere, some of the humid continental climates, typically in Hokkaido, Northern Honshu, Sakhalin island, Scandinavia , Nova Scotia, and Newfoundland are closer to the sea and is heavily maritime-influenced, with relatively cool summers and winters being just below the freezing mark. More extreme and inland humid continental climates found in northeast China, southern Siberia, the Korean Peninsula (except for the southern region in South Korea), the Canadian Prairies, and the Great Lakes region of the American Midwest, New England, and Central Canada combine hotter summer maxima and colder winters than the marine-based variety. Definition. Using the Köppen climate classification, a climate is classified as humid continental when the temperature of the coldest month is  below or and there must be at least four months whose mean temperatures are at or above . These temperatures were not arbitrary. In Europe, the average temperature isotherm (line of equal temperature) was near the southern extent of winter snowpack. In the United States, it is more common to use the isotherm instead. The average temperature was found to roughly be the minimum temperature necessary for tree reproduction and 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 : Associated precipitation. Within North America, moisture within this climate regime is supplied by the Great Lakes, 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. Vegetation. By definition, forests thrive within this climate. Biomes within this climate regime include temperate woodlands, temperate grasslands, temperate deciduous or evergreen forests, coniferous forests, and coniferous swamps. Within wetter areas, maple, spruce, pine, fir, and oak can be found. Fall foliage is noted during the autumn of deciduous forests. Hot summer subtype. A hot summer version of a  continental climate features an average temperature of at least in its warmest month. Since these regimes are limited to the Northern Hemisphere, the warmest month is usually July or August. High temperatures in the warmest month tend to be in the high 20s or low 30s °C (80s or low 90s °F), while average January afternoon temperatures are near or well below freezing. 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 Essex County, the core area of the Golden Horseshoe and  Greater Montreal) and portions of the central and eastern United States from 100°W 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. In the eastern United States Pennsylvania , Connecticut, Ohio, New York, Delaware and Massachusetts have some part of their state in this climate zone. In the Eastern Hemisphere, this climate regime is found within interior Eurasia, east-central Asia, and parts of India. Within Europe, the "Dfa" climate type is present near the Black Sea in southern Ukraine, the Southern Federal District of Russia, southern Moldova, Serbia, parts of southern Romania, and Bulgaria, but tends to be drier and can be even semi-arid in these places. In East Asia, this climate exhibits a monsoonal tendency with much higher precipitation in summer than in winter, and due  to the effects of the strong Siberian High much colder winter temperatures than similar latitudes around the world, however with lower snowfall, the exception being western Japan with its heavy snowfall. Tōhoku, between Tokyo and Hokkaidō and Western coast of Japan also has a climate with Köppen classification "Dfa", but is wetter even than that part of North America with this climate type. A variant which has dry winters and hence relatively lower snowfall with monsoonal type summer rainfall is to be found in northern China including Manchuria and parts of North China, and over much of the Korean Peninsula ; it has the Köppen classification "Dwa". Much of central Asia, northwestern China, and southern Mongolia have a thermal regime similar to that of the "Dfa" climate type, but these regions receive so little precipitation that they are more often classified as steppes ("BSk") or deserts ("BWk"). "Dsa" climates are rare; they are generally restricted to elevated areas adjacent to Mediterranean climate regions with a "Csa" climate well inland to ensure hot summers and cold winters. They are generally found in the highly elevated areas of south-eastern Turkey (Hakkâri), north-western Iran and parts of Central Asia. This climate zone  does not exist at all in the southern hemisphere, where the only landmass that enters the upper-middle latitudes, South America, tapers too much to have any place that gets the combination of snowy winters and hot summers. Marine influences preclude "Dfa", "Dwa", and "Dsa" climates in the southern hemisphere.