upslope fog

weather

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Last updated

July 16, 2026

Quick Summary

Upslope fog is a type of fog that forms when moist air flows up a sloping terrain. As the air rises, it cools due to adiabatic expansion, causing the water vapor within it to condense into tiny water droplets. This process creates a cloud at ground level, which we perceive as fog.12

This phenomenon is distinct from other fog types like advection fog (warm air over cold surfaces), steam fog (cold air over warm water), frontal fog (near weather fronts), radiation fog (ground cooling), and ice fog (extremely cold temperatures).2

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How Does Fog Form?
For example, upslope fog occurs when humid air is forced up the sides of hills or mountains. Advection fog forms when warm, moist air moves slowly over a colder surface, such as when warm air from the Gulf Stream blows over the cold Labrador Current, leading to…
Read More
For example, upslope fog occurs when humid air is forced up the sides of hills or mountains. Advection fog forms when warm, moist air moves slowly over a colder surface, such as when warm air from the Gulf Stream blows over the cold Labrador Current, leading to…
Read More