The scene can be as spectacular as a view from above showing only the tops of city skyscrapers poking through or as disorienting as a sheet of gray directly in front of you.
While common in some locations, fog can simply amaze us.
According to the Glossary of Meteorology from the American Meteorological Society, fog is a collection of water droplets suspended in the atmosphere in the vicinity of the earth's surface that affects visibility. Specifically, fog reduces visibility below 1 kilometer (or 0.62 miles).
Some Common Types of Fog
The most common form of fog, known as radiation fog, typically occurs on clear nights as the earth's surface cools moist air immediately above it. If just enough light wind is present – a couple of mph, at most – this chilled air can be gently stirred through a deeper layer, forming a deeper radiation fog.
Often in the fall, you'll see morning fog hug lower valleys of the Appalachians. This valley fog, really just a type of radiation fog, results from cold, dense air draining down mountain slopes at night, collecting in the valley floors, then forming as any other radiation fog described above.
Incidentally, let's dispel a myth. Fog does not burn off, per se.
As solar energy heats the ground near the fog's edge, vertical mixing brings drier air into the fog's edge, evaporating it. A typical ground fog will dissipate first at its edges, where its depth is more shallow, working its way toward the thicker center of the fog.
Sometimes fog forms when warm air moves over a cold surface. Warm air moving over snow-covered ground in winter and sea fog drawn inland over a cool land surface along the West Coast are two prime examples of so-called advection fog. Unlike radiation fog, advection fog can sometimes be seen as moving laterally along or near the ground.
When surface temperatures are below freezing, water droplets in a fog are supercooled, waiting to freeze on contact with any subfreezing surface. These freezing fog events can be dangerous not only for a reduction in visibility but also for a light accumulation of ice on roads, particularly bridges and overpasses.
At even colder temperatures, fog made up solely of tiny ice crystals will form. This ice fog is common in the winter months in parts of Alaska's interior, among other locations closer to the poles.
You may also notice steam fog from some lakes in the fall or early winter. Cold air overlaying warm air near the warm lake surface is an unstable configuration, lending itself to rising air. The mixing of cool air chills the warmer, more moist air immediately above the lake to allow condensation and a cloud to form. You can typically see wispy, vertical currents of fog rising from the lake.