The Foggiest Ideas Trivia Quiz

Answer: A cloud in contact with the ground

When it comes to clouds, fog is the most down to earth of the bunch (I will not apologize!). It typically forms at ground level when the air near the surface cools enough for water vapor to condense into tiny droplets. That's the stuff of clouds, and that's the stuff of fog, just lower where it can irritate us and create fabulous atmosphere for horror movies.

Unlike rain or snow, fog isn't precipitation. It doesn't "fall"; it just kind of hangs around, rising or settling based on the atmospheric conditions. Depending on the mood of the weather, it can be a light fog that makes you wax poetic or a thick carpet that makes you ponder the existence of your mailbox. Either way, it's simply a cloud with no real ambition.

Answer: The temperature at which air becomes saturated with water

Do you ever eat too much and cast your plate aside with an exclamation of "That's it! I'm full!"? Well, the dew point is the temperature at which the air says, "That's it, I'm full," and can't possibly hold any more water vapor. At this point, the moisture condenses into tiny droplets, which takes the form of dew if it's on the grass, or fog if it's hanging around in the air.

The dew point is a handy measure for humidity. The closer the air temperature is to the dew point, the stickier and ickier it feels. When they're the same... well, congratulations! You've reached maximum sogginess.

Answer: Particles in the air

Water vapor hates to form droplets all on its own. It's shy like that. Because of surface tension, it needs something to cling to, and since my bathroom mirror is not typically nearby, that "something" comes in the form of condensation nuclei, which are just microscopic particles floating around in the air. This can be dust, sea salt, smoke, volcanic ash, or any other hygroscopic bits that the liquified vapor can cling to. (Don't be afraid of "hygroscopic". It refers to anything that likes to absorb moisture from the air.)

Without these little helpers, you wouldn't have fog or clouds, just a very sad and confused atmosphere. So, yes. The next time you're caught in a fog bank, give a shout out to the dust motes in the air for making your morning commute feel like a scene from a gothic novel.

Answer: Density and visibility

The difference between fog and mist is a bit arbitrary, sort of like the difference between a lake and a pond. They're basically the same thing, but we like to split hairs. Fortunately, in the case of fog and mist, meteorologists actually give us rules. If visibility drops to under 1 kilometer (about 0.62 miles), congratulations, you're in fog. Anything clearer than that is mist.

Fog is a denser, more stubborn first cousin, with larger water droplets that like to sit around and cause traffic headaches. Mist, on the other hand, is lighter, more delicate, and often described as "romantic"... until you realize that fog is just mist that refuses to leave, and typically the kind where monsters and/or horror-movie villains prefer to hide.

Answer: Radiation fog

When the ground loses heat at night, it cools the air just above it down to the dew point, and water vapor condenses into what we call radiation fog. It's also nicknamed "ground fog," because it hugs the earth like a thick fluffy wet blanket. Fortunately, it usually burns off once the sun shows up and does its thing. If you don't want to deal with radiation fog, I recommend setting your alarm later.

Clear skies are essential for this type of fog to form, since clouds act like a big old thermal lid, trapping the heat and spoiling the effect.

Answer: Rime

Rime is fog's way of making your life extra treacherous in freezing weather. The tiny water droplets in fog freeze on contact with cold surfaces, building up into a thin, sometimes feathery-looking layer of ice. It can make trees look like they belong in a winter wonderland and power lines look like a Roland Emerick effect.

It's different from frost, which forms directly from water vapor, and from black ice, which is a serious driving hazard. Rime is more dramatic and maybe a little prettier if you're into feathery ice sheets on the grown. Regardless, nothing really excuses our species from taking the time to create another new word for ice.

Answer: Cold air moves over warm water

Steam fog, sometimes called sea smoke by the more poetic among our ranks, forms when cold air sweeps across warmer water. The water evaporates into the cold air, quickly condenses, and voilą: you've got yourself some creepy wisps of fog rising from the surface like something out of a pirate movie.

This phenomenon is most common in autumn and early winter, when lakes, rivers, and oceans are slow to surrender their precious summer warmth. You'll see it in the early morning, especially after a cold front has barged in overnight. The contrast between warm water and cold air creates a dramatic visual that makes it look like the water is exhaling.

Answer: Coastal areas

Advection is simply the sideways shuffling of air, and advection fog forms when warm, moist air drifts over colder ground or water, like fingers gently running down a cold window. The cooling causes the vapor to condense, creating the thick, rolling fog banks that coastal cities know well.

This type of fog often travels inland, especially when pushed by winds, and it tends to be persistent. Unlike radiation fog, which burns off with morning sun, advection fog can linger all day if the air stays put. It's the kind of fog that doesn't just visit... it moves in, annoys your neighbors, and reorganizes your silverware drawer.

If you've ever watched fog pour into San Francisco, that's advection fog. It's so reliable there, it contributes to the city's overall vibe and might as well have its own Instagram account. Okay, that's too subtle. While researching this, I found yet another sign that we're in the end times: not only DOES it have its own Instagram account, but it also has an X account, Facebook account, and of course its own web page. Do an Internet search for "Karl the Fog" for more information.

Answer: Fog oases

Fog oases are fascinating ecosystems where life sucks the water straight out of the air. In places like the coastal deserts of Chile and Peru, rain is a rarity, but fog drifts in from the ocean and provides the moisture plants and animals need to survive. Some plants have even evolved special shapes and surfaces to harvest the droplets directly.

These oases can look like miracles, patches of greenery sustained almost entirely by mist. It's proof that fog isn't just a nuisance on your morning commute. In some corners of the world, it's the only reason life exists.

Answer: Transmissometer

The transmissometer is the hero of foggy aircraft landings. It sits on opposite ends of a runway with a transmitter and a receiver. A beam of light is fired across, and the device measures how much light actually makes it to the other side. The less light received, the thicker the fog, and the more a pilot has to rely on instruments instead of eyeballs.

Modern airports often use a forward-scatter visibility sensor as well, which sends out near-infrared light in a cone. Water droplets scatter the beam, and the amount of scattering is measured to calculate just how far a pilot can see. It's cutting-edge precision designed to keep the planes moving safely.