Do sneezes freeze in cold weather?

May 1, 2017 9:17 PM

Smallest child asked this and I can't find a good answer for her reliably that doesn't sound like an urban legend. She is fascinated by how warm breath condenses in colder air and hot water freezes in the Arctic, so asked about sneezing and I'm stumped. Snot-related answers also appreciated!
posted by dorothyisunderwood to Science & Nature (13 answers total)

This is just from personal experience. I don't remember sneezing in cold weather, oddly, but I live somewhere where it can get cold enough that you can feel the snot freeze inside your nose as you breathe. It is grossly cool!
posted by spelunkingplato at 9:33 PM on May 1, 2017 [3 favorites]

Below about 10 degrees Fahrenheit you can feel the hairs on the inside of your nose hair freeze as soon as you step outside. I haven't really though much about sneezing outside, other than that if you sneezed into your glove or elbow that definitely gets wet and then freezes, too.

You can have neat frost buildup problems on facial hair and when it is that cold it is often much nicer to breathe through a balaclava if you are out for extended periods of time; that will get frosty, too, as will the edges of your hair if they're long and in the exhaust zone.
posted by charmedimsure at 9:39 PM on May 1, 2017 [1 favorite]

There are videos of spilled mugs of hot coffee freezing before they hit the ground in weather around -40F or so. So I'd be pretty sure that sneezes would freeze too.

Here's the first such video I found on youtube: here
posted by forza at 10:02 PM on May 1, 2017 [2 favorites]

Sure, but they leave your nose moving pretty fast and the particles are pretty small. Snot on your face will freeze, but you don't end up with a rigid chunk of sneeze it in front of your nose, just a bunch of miniscule ice particles, I think. That's why there's not a trove of awesome frozen sneeze videos out there; the frozen snot and dust you​ expel is not big enough to be visible on film.

Pics of friends at the South Pole show ice built up on their eyelashes. If it gets cold enough out, lots of things freeze that you wouldn't expect.
posted by potrzebie at 10:06 PM on May 1, 2017 [1 favorite]

When I was in grade school and it was really, really cold outside -- maybe -15F -- I discovered that my spit would make a loud crackling sound before it hit the ground.

I don't know why. Maybe it would freeze and then the frozen bubbles would implode?
posted by jamjam at 10:41 PM on May 1, 2017 [1 favorite]

As I recall from a few half-rememberd experiences at the South Pole, sneezing without a face covering in the -70s F isn't too exciting. The water vapor in your exhaled breath turns to fog, but it slows down pretty quickly and rises just like a normal breath. The droplets probably freeze, but that doesn't really change their behavior visibly. It's less neat looking than just exhaling a lung full of air quickly. But, I've never watched someone else sneeze in such weather. (& it never occurred to me until now to film it in slow motion.)

Sneezing repeatedly, or (worse) having a runny nose *inside* a balaclava, though, is absolutely disgusting. A thick layer of snowy frozen breath moisture is normal. After ten minutes outside everyone has a snow beard. It dries and disappears quickly once you take it off. A thick layer of frozen snot, however, doesn't go away. Taking off enough glove and face covering to use a tissue outside is both tedious and often painful, so you more or less just have to blow your nose into your balaclava. (Having a cold in the antarctic makes you appreciate laundry day in a new way.)
posted by eotvos at 10:47 PM on May 1, 2017 [30 favorites]

This might be a good question to ask the folks at the Mount Washington Observatory. They are the cold weather experts and have posted all kinds of fun videos of various shenanigans in the cold. There's a contact form on the website and they also have a Facebook presence where you might ask .

I know for a fact that snot freezes. Back when I did a lot of winter hiking and had a beard, after a couple hours above treeline in the winter I'd develop what we referred to as "snotcicles." In fact good winter mountaineering gloves will usually have a pad on the back of the wrist that is specifically for wiping snot from your nose.

A Google Image Search for "snotcicles" turns up lots of wonderful frozen snot images.
posted by bondcliff at 6:24 AM on May 2, 2017 [1 favorite]

She might find it interesting how in cold, dry air, after very sweaty exertion, if you strip off your outermost layers while you're still outdoors you can get a plume of evaporation-steam rising off your whole body like you're the Terminator just materialized from the future. It's especially visible at night, in good lighting, while the air is still.
posted by XMLicious at 6:45 AM on May 2, 2017 [2 favorites]

Said evaporation-steam is frequently visible coming off the heads of bald football players on cold days.
posted by Huffy Puffy at 6:58 AM on May 2, 2017 [1 favorite]

Sneezing in below -30C - -20C is just like sneezing. Yes, likely the snot/moisture bits are freezing, but they've already been expelled.

Something that might be more interesting is an image search for the term "frost beard" while running out in temps as mild as -8C the exercise keeps your body warm, and the requirement of lots of breathing keeps your lungs moist. Meaning one's exhaling tonnes of warm, moist air which will quickly condense. Any that condenses on your beard (and eyebrows!) quickly freezes and stays there.

"Dog frost beard" happens too (I run with my wife's dog), however google image search doesn't seem to have as many examples of dogs as they do people for that term.
posted by nobeagle at 6:58 AM on May 2, 2017

I grew up in the coldest city on earth. If you've seen videos of hot liquids disappearing into thin air with a woosh, they were probably shot there.

During winter, when it averages around -50 °C (which is about -60 °F) the snot question is a bit theoretical. You cannot leave your face uncovered outside - you would get a permanent frostbite pretty quickly - so you breathe inside a thick scarf or a face mask. It warms up from your breath so any snot situation becomes gross rather than interesting. Typically, you just try to hold the snot inside or swallow it (sorry).

To make up for the disappointment, I offer your child this gift: on a day that is sufficiently cold but not so cold that you would be able to make those swoosh videos, if you are a boy and you pee outside, the pee will freeze and you can break it off right from your peepee. (If you are a girl, you would not pee outside because removing clothing for even a couple minutes would freeze your bum off).

Bonus: if you close your eyes and exhale up for a few breaths, you can freeze your eyes shut and you'll have to really exert your eyelid muscles to pull your eyelashes apart so you can see again.

Note: warmer wikipedia temperature averages reflect global warming + cooking of data by the government in order to avoid paying double for people working outside during extra cold days.
posted by rada at 7:59 AM on May 2, 2017 [20 favorites]

I've seen it happen. It just looks like a slightly more visible spray. Below about -15 C, your breath will freeze on your own damn eyelashes and you'll feel the snot inside your nose freeze every time you breathe in.
posted by bizarrenacle at 2:23 AM on May 3, 2017

Said evaporation-steam is frequently visible coming off the heads of bald football players on cold days.

I've been caught steaming dozens if not hundreds of times. Usually after biking in cold weather or dancing myself silly in a club and then going outside to cool off. It's not always a subtle thing, either. A few times after working up a sweat dancing and going outside I'm practically generating my own fog bank or cloud system.

People seem to find it amusing, and it's a neat party trick.

Conversely if you've ever had me in your car after a brisk walk you already know I'll fog up every window in the car if it's even slightly cooler outside. This part is annoying and kind of embarrassing. It's almost impossible for me to be in a car without cracking a window.
posted by loquacious at 2:28 PM on May 14, 2017 [1 favorite]