Humid Continental Climate

A humid continental climate (Köppen prefix D and a third letter of a or b) is a climatic region typified by large seasonal temperature differences, with warm to hot (and often humid) summers and cold (sometimes severely cold) winters.

Precipitation is relatively well distributed year-round in many areas with this climate, while others may see a marked reduction in wintry precipitation and even a wintertime drought. Snowfall, regardless of average seasonal totals, 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 a very occasional tropical system. Though humidity levels are often high in locations with humid continental climates, the "humid" designation does not mean that the humidity levels are necessarily high, only that the climate is not dry enough to be classified as semi-arid or arid. Very few areas with a humid continental climate fall in the Dsa or Dsb categories; generally these are adjacent to Mediterranean climates where the elevation precludes such classification due to colder winters.

Humid continental climates tend to be found above 40° N latitude, 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.

The Köppen definition of this climate regarding temperature is as follows: the mean temperature of the coldest month must be below −3 °C (26.6 °F) (some climatologists prefer to use the freezing mark), 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.