Weather Science
Air Masses Explained: Maritime, Continental, Tropical, and Polar Air
What air masses are, how they get their temperature and moisture traits, and why air mass boundaries create fronts and storms.
Quick answer: An air mass is a large body of air with broadly similar temperature and moisture characteristics.
Source regions
Air masses take on traits from where they spend time. Air over oceans becomes more maritime and moist, while air over land can be drier.
Tropical source regions are warmer, and polar or Arctic source regions are colder.
Fronts form between them
When contrasting air masses meet, the boundary can become a front.
Fronts focus lift, wind shifts, clouds, precipitation, and sometimes severe weather.
Why it matters
Air mass changes explain many day-to-day weather swings: humid to dry, warm to cold, cloudy to clear.
Forecasters track air masses to understand storm potential and temperature changes.