Fog Page
(all photographs by J. Gerencher)

Fogs form when moist air is cooled, or when cool air has water vapor added to it.  In either case, the air near the Earth's surface becomes saturated with water vapor and droplets form.  Fogs are more common in certain regions than in others because one or more of the mechanisms of fog formation are more prevalent there.  

Radiation fog in Lehigh Valley, PA
Radiation fog on the valley floor during the early morning hours in
the Lehigh Valley, as seen descending from South Mountain on Interstate 78,
between Bethlehem and Easton, PA.

Advection fog inland from Oregon coast
Advection fog blown inland along the Oregon coast.

Advection fog in San Francisco, CA
Golden Gate Bridge enveloped in fog,
San Francisco, California