Change in weather occurs because air in the atmosphere is constantly _________and moving.

Change in weather occurs because air in the atmosphere is constantly **circulating** and moving. Air masses have similar temperatures and **humidity** levels which are determined by where they were **formed**.

**Frontal boundaries** form when two air masses meet. **Cold** fronts on a weather map are blue lines with triangles. **Warm** fronts on a weather map are red lines with semi-circles.

**Cold Front** occurs when the cold air moves under warm air and pushes it up where it cools and **condenses**, forming clouds. Big **temperature** differences between the warm and cold front could result in severe weather.