Continental (Group D) climates are found in most of the North American interior from about 40 °N to 70 °N. What climate characteristics is the continental group most likely to have?

• Temperature: The average temperature of the warmest month is higher than 10 °C (50 °F) and the coldest month is below −3 °C (−27 °F).
• Precipitation: Winters are cold and stormy (look at the latitude of this zone and see if you can figure out why). Snowfall is common and snow stays on the ground for long periods of time.

Trees grow in continental climates, even though winters are extremely cold, because the average annual temperature is fairly mild. Continental climates are not found in the Southern Hemisphere because of the absence of a continent large enough to generate this effect.

Humid Continental (Dfa, Dfb)

The humid continental climates are found around the polar front in North America and Europe.

In the winter, middle-latitude cyclones bring chilly temperatures and snow. In the summer, westerly winds bring continental weather and warm temperatures. The average July temperature is often above 20 ºC (70 ºF). The region is typified by deciduous trees, which protect themselves in winter by losing their leaves.

The two variations of this climate are based on summer temperatures.

• Dfa, long, hot summers: summer days may be over 38 ºC (100 ºF), nights are warm and the temperature range is large, perhaps as great as 31 ºC (56 ºF). The long summers and high humidity foster plant growth.
• Dfb, long, cool summers: summer temperatures and humidity are lower. Winter temperatures are below −18 ºC (0 ºF) for long periods.

Subpolar (Dfc)

The subpolar climate is dominated by the continental polar air that masses over the frigid continent. Snowfall is light, but cold temperatures keep snow on the ground for months. Most of the approximately 50 cm (20 inches) of annual precipitation falls during summer cyclonic storms. The angle of the Sun’s rays is low but the Sun is visible in the sky for most or all of the day during the summer, so temperatures may get warm, but are rarely hot. These continental regions have extreme annual temperature ranges.

The boreal, coniferous forests found in the subpolar climate are called taiga and have small, hardy, and widely spaced trees. Taiga vast forests stretch across Eurasia and North America.