 A weather front is the zone where two different air masses come together at the Earth's surface. Each air mass has its own temperature and humidity treats, which can cause turbulence at the front that creates clouds and storms. When a front passes over an area, it can impact the weather, bringing rain or snow, temperature changes, thunderstorms, gusty winds and tornadoes. A cold front happens when a cool air mass advances into a warm air mass. The heavier cool air pushes under the lighter warm air, causing it to rise up and produce clouds and thunderstorms. Warm fronts move quickly, bringing gusty winds and rapid temperature drops as they pass through. There can also be heavy rain with hail, thunder and lightning. A warm front occurs when a cold air mass is replaced with warm air that pushes up and over the cold air. Warm fronts move more slowly than cold fronts because the cold dense air is tougher to push over. Warm fronts bring humid, moist air, increased temperatures and light precipitation. Fronts move across the Earth's surface over several days, guided by high winds like jet streams, and their path can be changed by landforms such as mountain ranges.