Temperature Inversion

Temperature inversions are observed when the air temperature increases with height. Under normal weather conditions, the air temperature typically decreases with height. 

A classic example is when colder air settles into mountain valleys during times of stable, high-pressure weather conditions. Colder, more dense air pushes under the warmer, less dense air in the valley, which creates the inversion.

For places like Jackson Hole, inversions can lead to very cold temperatures and valley fog near the bottom half of the mountain, followed by much warmer temperatures (30+°F) and abundant sunshine as you climb to the upper half of the mountain. 

Temperature inversions can also trap polluted air in urban environments that have specific topographic features. Salt Lake City is one location that is known for bad air quality due to inversions during prolonged periods of stable, high-pressure weather conditions in the winter months. The inversion traps the polluted air, which is caused by emissions due to the burning of fossil fuels, as well as from agricultural and other sources.