It's spooky and neat. Really thick fog can reduce you to seeing only a few feet in front of you. It can be a real hazard to cars, planes and boats. There are two kinds of fog, advection fog and radiation, or ground fog.
Advection fog is common along the pacific coast of the United States.
Warm, moist air over the Pacific Ocean are blown inward. When that air moves over colder coastal waters, it cools quickly and fog forms. The fog is moved inland by the same westerly winds. Advection fog plays an important role in the life of California Redwood trees. The Redwood trees have very shallow roots.