Weather fronts — Earth science, 14–17 years
A weather front is a boundary where air masses with different temperatures and moisture meet. The way one air mass moves over or pushes under the other helps predict clouds, rain and changing temperatures.
A boundary between air masses
An air mass is a large region of air with fairly similar temperature and moisture. At a front, two unlike air masses meet but do not mix immediately. Warm air is usually lifted over denser cold air, and rising air can cool, condense and form clouds.
Why fronts matter
A forecast must explain why weather can change sharply over a few hours, rather than treating clouds and rain as isolated events. Fronts give meteorologists a useful moving boundary to track. Their shape and speed help connect pressure patterns with the weather people experience.
Following a cold front
A cold air mass advances towards warmer, moist air. Because cold air is denser, it pushes underneath and lifts the warm air quickly. The rising air cools, clouds grow tall and a short, heavy shower may occur. After the front passes, the air is often cooler and drier.
A front is not a wall
It is easy to picture a front as a sharp, vertical wall separating two skies. That seems reasonable because weather maps draw a clear line. In reality, a front is a sloping transition zone, often hundreds of kilometres wide, where temperature, wind and moisture change gradually.
Everyday forecasts
Weather services mark fronts on maps to warn about rain, strong winds, storms or sudden temperature changes. The information can guide travel, farming, outdoor work and aviation. A front raises the likelihood of certain conditions, but local hills, coasts and timing still affect what happens at one exact place.
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