Continental climates often have a significant annual variation in temperature (hot summers and cold winters). They tend to occur in the middle latitudes (40 to 55 north), within large landmasses where prevailing winds blow overland bringing some precipitation, and temperatures are not moderated by bodies of water such as oceans or seas unlike temperate climates. Continental climates occur mostly in the Northern Hemisphere, which has the kind of large landmasses on temperate latitudes required for this type of climate to develop. Most of northern and northeastern China, eastern and southeastern Europe, Western and north western Iran, central and southeastern Canada, and the central and northeastern United States have this type of climate. Continentality is a measure of the degree to which a region experiences this type of climate.
In continental climates, precipitation tends to be moderate in amount, concentrated mostly in the warmer months. Only a few areas—in the mountains of the Pacific Northwest of North America and in Iran, northern Iraq, adjacent Turkey, Afghanistan, Pakistan, and Central Asia—show a winter maximum in precipitation. A portion of the annual precipitation falls as snowfall, and snow often remains on the ground for more than a month. Summers in continental climates can feature thunderstorms and frequent hot temperatures; however, summer weather is somewhat more stable than winter weather.
Annual precipitation in this zone is usually between 600 millimetres (24 in) and 1,200 millimetres (47 in), most of it in the form of snow during winter. The timing of intermediate spring-like or autumn-like temperatures in this zone vary depending on latitude and/or elevation. For example, spring may arrive as soon as March in the southern parts of this zone or as late as May in the north. Summers are warm or hot while winters are below freezing and sustain frost.
Most such areas fit Köppen climate classifications of Dfa, Dwa having hot summers (mean temperature of the warmest month above 22 °C; "w" indicating very dry winters characteristic especially of China) or Dfb or Dwb with warm summers (mean temperature below 22 °C). Dry summer continental climates (Dsa and Dsb) exist in high altitude areas near Mediterranean climates. In some cases, the semi-arid climate classification of BSk and the desert climate of BWk can also be considered to be continental as long as it has cold winters, though it isn't by the Köppen classification. The definition of this climate regarding temperature is as follows: the mean temperature of the coldest month must be below 0 °C (32.0 °F) and there must be at least four months whose mean temperatures are at or above 10 °C (50 °F).
Continental climates exist where cold air masses infiltrate during the winter from shorter days and warm air masses form in summer under conditions of high sun and longer days. Places with continental climates are as a rule are either far from any moderating effect of oceans or are so situated that prevailing winds tend to head offshore. Such regions get quite warm in the summer, achieving temperatures characteristic of tropical climates but are colder than any other climates of similar latitude in the winter.
In the Köppen climate system, these climates grade off toward temperate climates equator-ward where winters are less severe and semi-arid climates where precipitation becomes inadequate for tall-grass prairies. In Europe these climates may grade off into oceanic climates in which the influence of cool oceanic air masses is more marked toward the west. The subarctic climate (Köppen: Dfc/Dfd), with very cold, long and dry winters, but with at least one month above 10 °C (50 °F), might be considered a sub-type of the continental climate.