Hot-summer Humid Continental Climate (Dfa)

Hot-summer Humid Continental Climate (Dfa)


Dfa: D = Contiental  f = fully humid  a = Hot summer (No dry season)

humid continental climate is a climatic region 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 can have drier or dry seasons. 


Koppen climate map Dfa

Humid continental climates: Hot or very warm summer sub-types Dfa, Dwa, and Dsa. Source Wikicommons. Authors: Peel, M. C., Finlayson, B. L., and McMahon, T. A.
(University of Melbourne) 2011.

A hot summer version of a continental climate features an average temperature of at least 22 °C in its warmest month. Since these regimes are limited to the Northern Hemisphere (the Southern Hemisphere has no large land masses isolated from the moderating effects of the sea within the middle latitudes), 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, 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 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 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 climate type is present near the Black Sea in southern Ukraine, 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. The 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 has 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).

Flight safety and planning considerations

Low pressure systems bring low cloud, precipitation, strong winds and associated turbulence. Contaminated runways and strong cross-wind conditions increase risk of runway excursions. In-flight icing in frontal cloud can be a threat to aircraft safety, especially in the winter. High ambient temperatures in summer can have a significant and limiting impact on aircraft and human performance, as well as causing significant maintenance issues. Thunderstorms can occur in the spring (severe possible) and summer. See the related articles on Hot Weather Operations and Hot and High Operations.

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