What Is a Weather Front? Cold, Warm, and Occluded

What Is a Weather Front?

A weather front is the boundary between two different air masses — one warm, one cold. Because these air masses have different temperatures, humidity, and densities, interesting weather happens where they meet.

Cold Front

A cold front occurs when a mass of cold air advances and pushes under warmer air.

• Before: Warm, humid, possibly hazy
• During: Rapid temperature drop, heavy rain or thunderstorms, gusty winds
• After: Cooler, drier, clearing skies

Cold fronts move fast (up to 50 km/h) and produce sharp, short-lived weather changes.

Warm Front

A warm front occurs when warm air slides up and over retreating cold air.

• Before: Increasing clouds (cirrus → altostratus → nimbostratus), gradual pressure drop
• During: Light to moderate rain over a wide area, fog possible
• After: Warmer temperatures, clearing skies, higher humidity

Warm fronts move slowly and produce prolonged, lighter precipitation.

Occluded Front

When a fast-moving cold front catches up to a warm front, it lifts the warm air entirely off the ground. This creates an occluded front with characteristics of both — extended cloud, mixed precipitation, and complex wind shifts.

Stationary Front

When neither air mass advances, the front stalls. Stationary fronts bring lingering clouds, drizzle, and grey skies that can persist for days.

How to Spot an Approaching Front

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Watch for fronts in your forecast on Weather Tomorrow.