1. Air masses are large bodies of air that form over a specific region of the Earth's surface. 2. They are typically formed when air remains stationary over a particular area for an extended period of time, allowing it to take on the characteristics of that region. 3. Factors such as temperature, humidity, and pressure influence the properties of the air mass as it forms. 4. For example, if an air mass forms over a warm ocean, it will likely be warm and moist. 5. Conversely, if an air mass forms over a cold landmass, it will be cold and dry. 6. Once formed, air masses can move and interact with other air masses, leading to changes in weather patterns.