Point out that air masses are described in terms of temperature and humidity. Air masses near the North Pole are very cold. Air masses near the equator are very warm. Air masses are large amounts of air. They can be hot or cold.
Air masses can also be wet or dry.
Deserts are hot, dry places. Six air masses push into each other near North America. There are three cold air masses and three warm air masses. Give each student a copy of an outline map of North America. Have them identify the six air masses in the geographical areas of North America and label them a - f on the map.