A cold front brings a sharp drop in temperature and often thunderstorms. It forms when a cooler, denser air mass advances beneath warmer air, forcing the warm air upward along a sloping boundary.
The rising warm air can cool, condense, and produce vertically developed clouds, including cumulonimbus. When moisture and atmospheric instability are sufficient, the front may generate a narrow line of heavy showers, lightning, hail, strong winds, or even tornadoes. Temperature changes across particularly strong fronts can exceed 30°C.
Cold fronts usually move faster and produce more abrupt weather changes than warm fronts. On weather maps, they are shown as a blue line marked with triangles pointing in the direction of movement. A warm front, by contrast, generally brings a more gradual temperature rise and often broader, steadier precipitation.
A cold front does not guarantee a thunderstorm: dry air or weak instability may bring only wind, clouds, or a quick temperature drop. Occluded fronts combine characteristics of warm and cold fronts, while stationary fronts show little movement.