How’s the weather? That depends on what kind of air mass is over your region. Big masses of air that share moisture, temperature, and other qualities usually travel in big chunks. These masses can cover thousands of square miles.
An air mass is most like the Earth surface over which it forms. Warm, wet areas like the Gulf of Mexico make warm, humid air masses. Cold, dry areas like northern Canada make cold, dry air masses. Air masses are called high pressure systems or highs. That’s because the air in them is under high pressure. It’s like air in a bicycle tire. Highs usually bring stable weather. It may be very cold or very warm, depending on the season. But it doesn’t last forever. Air masses are always moving. They bump into each other as they travel around the globe.
