As a child, foggy mornings frightened me, and attempts to comfort me by calling them “fallen clouds” only thickened my anxiety. It was quite simply abnormal. Get me outa here!

Where I now live, I wouldn’t be surprised to see that we have more than a hundred foggy days a year. Many of those, it burns off early, but on others, we are caught in gray for what can extend for weeks. Maybe I need to start counting.

Still, as one Navy commander exclaimed, “You don’t have your share of fog. You have everyone’s!”

That said, let’s get more specific.

1. Technically, it is a ground-level cloud. Water vapor, which is invisible, turns into tiny droplets that hang in the air. That happens in very, very high humidity, wherever the temperature falls below the dew point. Not that it’s dew, either.
2. In order for fog to form, dust or some kind of pollution needs to be in the air. Water vapor condenses around these microscopic solid particles. Sea fog, which shows up near bodies of salty water, is formed as water vapor condenses around bits of salt.
3. Its hazy and ethereal atmospheric marvel has inspired artists, writers, poets, and even lovers, and has a profound impact on various aspects of nature and human emotions.
4. It’s not the same thing as mist. Fog is denser, more massive, thicker. There are more water molecules in the same amount of space in a fog.
5. Fog cuts visibility down to one kilometer or roughly a half-mile, meaning it prevents you from seeing further away that from where you’re standing. Mist can reduce visibility to between up to a mile.
6. One kind of fog is identified as radiation, when heat rising from the ground into cooler air than the air above it. Another is advection, when warm air blows across a cooler surface and condenses. It’s especially common on the west coast of the U.S. Hello, San Francisco. Upslope or orographic happens when warm air blows up a slope, such as the face of a mountain, and then cools “adiabatically.” It’s also called valley fog, when warmer air is trapped by mountains and much colder air above. Typically, it’s a winter phenomenon. And evaporation occurs when warmer water evaporates into cooler air.
7. Don’t confuse it with smoke, even if London’s famed “fog” was really industrial-era air pollution. Well, that complicates on fashion-coat label.
8. Fog enhances acoustic experiences. I can definitely hear the fog horn better when there’s fog and it did create the eerie experience of hearing voices from a ship we couldn’t see as it came to the pier.
9. It’s more common in coastal areas, due to temperature differences between the water, air, and land. As I was saying about our encounters here?
10. It can help mitigate high temperatures and reduce heat stress. Or turn everything into a steam bath. But it can also freeze into delicate layers of crystal across a landscape or treacherous conditions on boats, airplanes, cars and trucks. Make for slippery walkways, too.

Wherever you are, look for the fog bow, too, like a rainbow within a cloud.