When hot and cold air collide, the warm air rises above the cold, forming a low-pressure zone. Warm air cools as it rises in altitude, causing the liquid in it to condense and produce clouds and rain. Cool air rushes in to fill the low pressure zone, pushing warm air higher and producing a cycle that can result in strong winds and storms.
A front is the area where a warm and cold air mass collide. The direction of cold and warm air circulation determines the intensity of meteorological conditions along a front. When moving warm air collides with a cold air mass that is stationary, the warm air rises gradually, generating drizzle and light rain. The consequences are more severe when cold air collides with a stationary warm air mass. The cold air accelerates the rise of the warm air mass, resulting in huge, occasionally severe thunderstorms with torrential rains. Before the storm can disperse and calmer skies dominate, the air masses must attain equilibrium.
The sun’s uneven heating of the Earth causes warm and cold air masses. Warmer air masses form in the tropics, whereas colder air masses form at the poles.