Polar air masses are cold and originate close to the poles, or over continents during the winter months.

Polar Continental air masses are cold and originate over land masses during the winter months or over cold polar oceans. Moisture within this type of air mass will be low and temperatures can reach extremely cold levels.

Polar Maritime air masses are cool and moist. Temperatures will be cold in this type of air mass, but not as cold as the Polar Continental air. The high moisture content of the Polar Maritime air mass keeps the temperature warmer than continental polar air masses.

Notice the source regions of the 2 types of polar air masses.