A warm front occurs when a cold air mass retreats and is replaced by a warm air mass. Warm fronts typically bring some form of precipitation to the area.
Rain and stormy weather is most likely along the border where the warm and cold fronts meet. The differences in temperatures often cause storms. In the winter months, this collision can lead to severe weather. Warm fronts with more stable air produce less rain than fronts with unstable air.
When a warm front stalls out over a particular section of the country, it can lead to days of torrential downpours. On weather maps, warm fronts are represented by red half-circles. As the front progresses, temperatures in the area get warmer.