Climate: Midlatitude, Severe

Humid Continental

Regions with a humid continental climate have a large annual temperature range and four distinct seasons with mild to hot summers and long, severe winters. Humid continental is more temperate than the subarctic type due to its lower latitudes, around 40° N to 55° N. Mean annual precipitation typically ranges from 50 to 100 cm (centimeters), or 20 to 40 in. (inches), but this average usually decreases with increasing latitude. Proximity to the shoreline also influences precipitation, so in the United States and Southern Canada, for instance, precipitation decreases with increasing distance from the Atlantic shoreline, demonstrating reduced moisture content in the atmosphere.

Humid continental climates have the Köppen letter codes of Dfa, Dfb, Dwa, and Dwb. Dfa and Dwa are characterized by hot summers, while Dfb and Dwb have mild summers. The “f” and “w” refer to precipitation, with “f” meaning consistent monthly precipitation (=6 cm) and “w” meaning a relatively dry winter season.

In the hot summer zones (Dfa and Dwa), January temperatures typically average below 0 °C (32 °F) and July temperatures average between 18 °C (65 °F) and 24 °C (75 °F). Weather in the summer is often humid, and severe thunderstorms that produce hail and/or tornadoes can occur. North of these zones are areas with mild summers (Dfb and Dwb). Here, the warmest months do not exceed 22 °C (72 °F) on average, and winters are more severe, with greater amounts of snowfall.

A large proportion of the population of the United States, Canada, Eastern Europe, and Asia live in humid continental climates, mostly along the eastern part of these continents. Humid continental regions with hot summers include the Eastern and Midwestern United States, from the Atlantic coast to approximately the [Page 440]100th meridian; East Central Europe; Northern China; and Northern Korea. Regions with mild summers include the New England and Great Lakes regions of the United States, South and Central Canada, Scandinavia, Eastern Europe, and Russia.

Figure 1 World Köppen map of microthermal “D” climates. Humid continental and subarctic climates are only found in the Northern Hemisphere. Subarctic climates are the more severe of the two since they are north of humid continental climates.

Source: From Koppen classification worldmap D. (2006). Retrieved January 10, 2010, from http://commons.wikimedia.org/wiki/File:Koppen_classification_worldmap_D.png. Reprinted with permission.

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