# Freezing Fog Warning? **URL:** \ **Category:** Factual Questions\ **Created:** [December 23, 2010, 5:22am UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158 "2010-12-23T05:22:35Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [December 23, 2010, 5:22am UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/1 "2010-12-23T05:22:35Z")
We recently moved from California to Western Montana and are enjoying the seasonal weather… even the winter cold and snow. On the news tonight they announced a “freezing fog warning” for tomorrow morning. Freezing fog? I didn’t know fog could freeze. So what should I expect tomorrow? What does freezing fog look and feel like? And why is it considered dangerous to drive in? ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [December 23, 2010, 5:35am UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/2 "2010-12-23T05:35:48Z")
The water droplets in the fog freeze on contact with solid surfaces causing lots of ice to form. ---
**Author:** ![Cat\_Whisperer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cat_whisperer/32/4839_2.png) [@Cat\_Whisperer](https://boards.straightdope.com/u/Cat_Whisperer)\ **Post date:** [December 23, 2010, 5:45am UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/3 "2010-12-23T05:45:00Z")
That’s what I was going to say - the fog freezes ON everything. It makes driving dangerous because of the thin layer of ice on everything - just enough to grease things up. We don’t get freezing fog often, but I seem to recall it is a miserable type of weather - cold and moist is a Very Bad Thing. ---
**Author:** ![Lamar\_Mundane](https://avatars.discourse-cdn.com/v4/letter/l/85f322/32.png) [@Lamar\_Mundane](https://boards.straightdope.com/u/Lamar_Mundane)\ **Post date:** [December 23, 2010, 6:11am UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/4 "2010-12-23T06:11:52Z")
> [@Richard\_Pearse](#): > > The water droplets in the fog freeze on contact with solid surfaces causing lots of ice to form. Yes, the water in fog needs something non-gaseous to attach to to transition from a vapor to a liquid. It will remain vapor even in sub-freezing temps. One quibble - it’s usually not a big problem, and it makes everyting look super awesome when the fog lifts and the sun shines. It’s not like freezing rain, which can be a killer. Your best precaution is to have a full resevoir of windshield washer fluid, because it will ice up your windshield in a big hurry. ---
**Author:** ![Twoflower](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twoflower/32/22_2.png) [@Twoflower](https://boards.straightdope.com/u/Twoflower)\ **Post date:** [December 23, 2010, 7:05am UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/5 "2010-12-23T07:05:01Z")
Freezing fog can happen in California, too. Happens some times in the Sierra foothills, when the cold mountain air overlaps with the valley fog. Roads get _very_ slick when the fog droplets freeze into a smooth layer on the asphalt. ---
**Author:** ![Roland\_Orzabal](https://avatars.discourse-cdn.com/v4/letter/r/c2a13f/32.png) [@Roland\_Orzabal](https://boards.straightdope.com/u/Roland_Orzabal)\ **Post date:** [December 23, 2010, 7:35am UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/6 "2010-12-23T07:35:10Z")
Now that the question’s been answered: am I the only one who had never heard this term before, and was picturing some kind of Ice-Nine thing? ---
**Author:** ![Gary\_Robson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gary_robson/32/3448_2.png) [@Gary\_Robson](https://boards.straightdope.com/u/Gary_Robson)\ **Post date:** [December 23, 2010, 6:28pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/7 "2010-12-23T18:28:54Z")
I hate driving in freezing fog, as it makes for very slick roads and a sheet of ice on the outside of the car. On the other hand, I love waking up the morning after a freezing fog to see the patterns of ice crystals that have formed on the trees and fences and weathervanes. ---
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [December 23, 2010, 6:45pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/8 "2010-12-23T18:45:06Z")
Thanks everyone! Now I know… ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [December 23, 2010, 6:49pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/9 "2010-12-23T18:49:26Z")
> [@Roland\_Orzabal](#): > > Now that the question’s been answered: am I the only one who had never heard this term before, and was picturing some kind of Ice-Nine thing? The phenomena isn’t new, obviously, but from a terminology perspective I’d never heard of it either until the last couple of years. But then again, that might just be my lack of attention to things. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [December 23, 2010, 7:42pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/10 "2010-12-23T19:42:35Z")
I drove through 100+ miles\* of that stuff getting from Albuquerque to Denver last night. It was freezing on the windshield and mirrors, but the roads were still just warm enough not to ice, thank frog. \*Literally from just south of Las Vegas, NM all the way to the top of Raton pass, and some other long stretches as well. Raton pass was incredable, 35 mph in dense fog in NM, and then totally clear the instant we got into Colorado. Fog again before we got to Walsenburg though. ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [December 23, 2010, 7:47pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/11 "2010-12-23T19:47:29Z")
It could also be an [ice fog](http://en.wikipedia.org/wiki/Ice_fog) warning. Ice fog is common in areas where there is a localized inversion of warmer and colder air. Fairbanks, AK for example is a place where this happens frequently, and where my experience of it took place. It can be dense enough that one cannot see more than a few feet. ---
**Author:** ![fachverwirrt](https://avatars.discourse-cdn.com/v4/letter/f/94ad74/32.png) [@fachverwirrt](https://boards.straightdope.com/u/fachverwirrt)\ **Post date:** [December 23, 2010, 9:01pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/12 "2010-12-23T21:01:36Z")
It’s called [rime](http://en.wikipedia.org/wiki/Rime_ice). It’s particularly prevalent on Mt. Washington, NH, where you get stuff like [this](http://scenicnh.photoshelter.com/image/I0000teA5Hg5ZfZg). Yours, uh, probably won’t be as extreme. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [December 23, 2010, 9:10pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/13 "2010-12-23T21:10:43Z")
> [@Lamar\_Mundane](#): > > Yes, the water in fog needs something non-gaseous to attach to to transition from a vapor to a liquid. It will remain vapor even in sub-freezing temps. Technically, the water in fog are in a non-gaseous state. ---
**Author:** ![aerodave](https://avatars.discourse-cdn.com/v4/letter/a/f08c70/32.png) [@aerodave](https://boards.straightdope.com/u/aerodave)\ **Post date:** [December 23, 2010, 9:14pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/14 "2010-12-23T21:14:09Z")
> [@Lamar\_Mundane](#): > > Yes, the water in fog needs something non-gaseous to attach to to transition from a vapor to a liquid. It will remain vapor even in sub-freezing temps. If I may be pedantic…the water in fog is already a liquid. The droplets are discrete packages of floating liquid. It’s easy to think of fog as a vapor, but it’s actually a colloid, or aerosol, of liquid (water) suspended in a gas (air). ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [December 23, 2010, 10:15pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/15 "2010-12-23T22:15:47Z")
> [@fachverwirrt](#): > > It’s called [rime](http://en.wikipedia.org/wiki/Rime_ice). > > It’s particularly prevalent on Mt. Washington, NH, where you get stuff like [this](http://scenicnh.photoshelter.com/image/I0000teA5Hg5ZfZg). > > Yours, uh, probably won’t be as extreme. Cool stuff. I have a photo here someplace of a road grader completely encased in rime ice. Coastal Alaska is a wild place. ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [December 23, 2010, 10:42pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/16 "2010-12-23T22:42:03Z")
we call it hoar frost in Saskatchewan. ---
**Author:** ![Neidhart](https://avatars.discourse-cdn.com/v4/letter/n/bbe5ce/32.png) [@Neidhart](https://boards.straightdope.com/u/Neidhart)\ **Post date:** [December 23, 2010, 11:11pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/17 "2010-12-23T23:11:47Z")
I’ve seen rime when I visited Niagara Falls in the winter. It was fun prying the long, thin crescent-shaped ice chunks off the railings and throwing them into the river where they’d break apart with a POP! ---
**Author:** ![Cat\_Whisperer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cat_whisperer/32/4839_2.png) [@Cat\_Whisperer](https://boards.straightdope.com/u/Cat_Whisperer)\ **Post date:** [December 24, 2010, 5:21pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/18 "2010-12-24T17:21:17Z")
> [@Northern\_Piper](#): > > we call it hoar frost in Saskatchewan. Oh, we get that stuff all the time! I didn’t know another name for hoar frost was freezing fog! Yeah, hoar frost is beautiful. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [December 24, 2010, 11:14pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/19 "2010-12-24T23:14:36Z")
Hoar frost is the ice while freezing fog is the weather that produces it. ---
**Author:** ![Critical\_Mass](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@Critical\_Mass](https://boards.straightdope.com/u/Critical_Mass)\ **Post date:** [December 24, 2010, 11:32pm UTC](https://boards.straightdope.com/t/freezing-fog-warning/565158/20 "2010-12-24T23:32:54Z")
If you want to strike fear into the heart of an aviator, say the words freezing fog. An aircraft flying through freezing fog is usually relatively close to the ground. If the airplane is on approach to an airport and flying through freezing fog it is gradually accumulating ice on the control surfaces, degrading handling characteristics, increasing overall weight, the pilots are suffering from reduced visibility and all this at a critical phase of flight while the airspeed is slowing and precision handling is imperative. Not nice stuff to airplanes. [Next page](https://boards.straightdope.com/t/freezing-fog-warning/565158.md?page=2)