Weather Science
Temperature Inversion Explained: Why Air Gets Trapped Near the Ground
How temperature inversions form, why they trap fog, smoke, pollution, and cold air, and why valleys often feel the strongest effects.
Quick answer: A temperature inversion happens when warmer air sits above cooler air near the surface, limiting vertical mixing.
Normal vs inverted
Normally air tends to cool with height. In an inversion, that pattern flips for a layer, making the lower atmosphere more stable.
Stable air acts like a lid that keeps surface air from mixing upward.
Common impacts
Inversions can trap fog, wildfire smoke, vehicle pollution, and cold air in valleys or urban basins.
They can also create freezing rain setups when warm air aloft melts snow and shallow cold air near the ground refreezes it on contact.
When it breaks
Sun heating, stronger wind, a front, or storm system can mix the air and break the inversion.
Until then, air quality and visibility may stay poor.