A warm front is the transition area where a mass of warm air moves to replace a mass of cold air. On a weather map, a warm front is usually drawn using a solid red line with half circles pointing at the cold air that will be replaced. Warm fronts usually move from southwest to northeast. A warm front can initially bring rain, followed by clear skies and warm temperatures. On the other hand, a cold front is usually drawn using blue.

Source: National Oceanic and Atmospheric Administration