(cP) Continental Polar Air Mass
Forms over Northern Canada and brings extremely cold weather to US in winter and cool dry weather in the summer.
(mP) Maritime Polar Air Mass
Forms over the North Pacific and brings cool, very wet weather to the Pacific Coast and fog in summer. Also forms over North Atlantic Ocean and brings cloudy weather and precipitation to New England in winter and fog in summer.
(mT) Maritime Tropical
Develop over warm areas over the Pacific (mild)
Others develop over the Atlantic and Gulf of Mexico and bring hot humid weather in summer, hurricanes and thunderstorms.
Continental Tropical (cT) form over the desert of Northern Mexico and SW United States brings clear, dry, hot weather northward in summer.
When a warm air mass is caught between two colder air masses - cool temperatures and large amounts of rain or snow.
When a cold air mass meets a warm air mass and remain separated. Brings many days of cloudy, wet weather.
Areas that have lower pressure than the surrounding areas do. Air masses come together and rise. Stormy weather occurs.