It’s May, the coldest month of the year, so it’s the perfect time to talk about a cold-weather car phenomenon I bet we’ve all wondered about! Well, that’s not entirely true, I suppose. It’s hot, and I can’t remember when I last saw anything resembling ice on the roads, but that didn’t stop Autopian reader Geir from asking the important question: why the hell do cars that have icy road warnings ding their little warning chimes at 37° to 40° F, when we all know damn well that water freezes at 32°? What’s going on here? Let’s find out.
First, you know what I’m talking about, right? On most cars made since, oh, 2000 or so, there’s a little light on the dashboard that will come on, usually accompanied by some sort of audio cue like a ding or beep or chime or, if you’re lucky, gong, and usually the light or icon will be in the shape of a little snowflake. The temperature that this light may come on tends to vary somewhere in the high 30° to 40° zone, with the most common temperature seeming to be 37°. As you may have guessed, people have been wondering about why this particular temperature was picked for quite a while. Here’s a nice lady who works for Mini talking about just this thing:
I like the sassy way she ends the video by saying “and that’s icy warning,” too. This video suggests that 37° was chosen because that’s the temperature that ice can form on bridges and other road surfaces. This explanation sort of makes sense, because it is absolutely true that bridges do ice before roads, as everyone’s favorite Joint Toll Bridge Commission, the Delaware one, reminds us:
Why do bridges freeze before a road? The reason bridges freeze before other surfaces is basic physics. Four factors contribute to rapid icing conditions on bridges:
• Exposure of the structure to air from below and above
• The absence of soil that provides an insulating effect on non-bridge road surfaces
• The tendency of bridges to be situated over cold spots like rivers and deep ravines
• The use of construction materials like steel and concrete that do not retain heat When freezing winds pass over and below a bridge, the structure loses heat from every side.
Bridges inherently lack the ability to trap any heat, so they will freeze shortly after atmospheric temperatures hit the freezing point. In contrast, most roads are made of asphalt, a material less-prone to heat loss. Roadways also can take advantage of the insulating and warming effects from the soil below them.
Now, this doesn’t mean that water somehow, magically knows it’s on a bridge and decides to ice up five degrees sooner for shits and, where applicable, giggles. Water doesn’t work that way. But, if the car’s temperature sensor hits a number like 37°, then it’s likely that the temperature could be less in different places, or surfaces may have lower temperatures from wind chill or evaporative cooling, and a buffer of five degrees is just a prudent precaution.
I reached out to Kia, who chimes their snowflake warning on the upper side of the spectrum, at 40°, and the buffer zone/abundance of caution explanation was confirmed:
Spoke to our Product Planning department, and “Bridge freezes before roadway” is a perfect example. Basically, it’s exercising an abundance of caution for varying / dynamic weather factors and roadway situations.
So, really, there’s nothing magical about 37° or 40° or anything like that–the reason the warning is not right at the actual freezing temperature of water is because the world is an imprecise place, and it makes sense to give a little wiggle room and prepare for freezing temperatures and icy roads before they actually are encountered. That’s the whole point of a warning after, all, isn’t it? Better to be made aware that ice is likely to happen before it actually does than given no warning at all.
This all makes a lot of sense, really. In hindsight, I wonder why I was ever so baffled! Well, me and Geir.
My BMW did this, and my two thoughts about it were always “37 is oddly specific”, and “thanks for the warning, not sure I would have noticed the cold otherwise.” The Alfa Romeo has a much more pragmatic response to it being really cold out–it automatically turns on my seat heater.
Neither my 2019 Fusion nor my previous 2010 Focus do this. Not sure if Ford is unconcerned with my safety, or trusts I’m well aware it’s fucking cold out.
I’ve owned 4 modern Fords and none of them did this so I think they truly don’t care.
My wife’s Subaru and my KTM 990 both warn about this though.
Surprised Volvo didn’t make them as every Ford-era Volvo I’ve ever driven does.
My Ford Siesta doesn’t care neither does my Honda motorcycle from the last century, however my wife’s Subaru Impreza does as does my Kawasaki Versys 650. I have lived in Canada and been conscious long enough that the warning is somewhere between an annoyance and a joke.
How odd. I had a 2006 Focus (AU market) that had an orange snowflake on the dash at 4°C (40°F) and a red snowflake at 0°C (32°F) or lower.
Neither does my 2015 Kia Soul. It does have a thermometer that’s in the gauge cluster, but assumes the driver can deduce whether that temp is close to freezing.
Can we get a follow up article on how to disable this stupid feature?
It’s a “no shit, Sherlock!” For us that drive where there are actual winters.
The only effect wind chill has on inanimate objects, such as car radiators and water pipes, is to more quickly cool the object to the current air temperature. The object will NOT cool below the actual air temperature. But yeah you also need the warning as the ground can be cooler than the air, living in northern Alberta that light is on six months a year
Right, air having the lowest specific heat, it can suddenly be many degrees, or even many tens of degrees warmer than the ground. It’s funny you specifically mentioned “pipes” and wind chill because I had a situation where a pipe would freeze in my Minnesota rental house only when it was windy. “But houses don’t get wind chill!” I finally discovered that there was a crack in the basement wall that was allowing the cold air in directly onto the pipe.. 1928 house problems..
Wind chill does affect inanimate objects the a) produce their own heat, or b) have residual heat.
So, fill two glasses of water, indoors, at 72 degrees. Place both outside on a winter day, one in the wind and one protected from the wind.
The wind will cause more air molecules to flow around the windy glass, which will remove heat from the water faster. Once the two glasses of water have both lost all their heat, and equalized to the ambient temperature, then the wind no longer has any effect.
Sure, but in the context of this article if you put both glasses of water outside in 37 degree temperatures neither will ever freeze. Windchill cannot make a 37 degree glass of water freeze.
Is that an Aston Lagonda dash???
Yes, but notice that the dash display readouts are photoshopped in. No Lagonda dash was capable of displaying anything from the factory.
COTD submission right there.
you thought it’s bad when accountants design auto features?
this is lawyers designing features!
same dynamic results in my radio controls and reverse camera being disabled for a few seconds when i start up because honda’s lawyers feel compelled to warn me to pay attention to my surroundings.
please stop helping me!
fwiw, the thermometer used is in the intake – primary use is for the ecm to know what the temperature is so it can adjust mixture/timing. icy condition warning is an add-on.
also, fwiw, i get the icon on my bmw motorcycle display at 34F.
37F…not 34F
I’m a lawyer in the auto industry. This comment is funny to me because (in my experience) we are absolutely not more tightassed than the engineers working in safety-related roles. Such a thing is simply not conceivable.
fair enough
The thermometer used for the temp readout on your dash is not in the intake, but rather a separate one away from the heat soaked engine compartment such as behind the bumper cover or near the cowl.
“…when we all know damn well that water freezes at 32°…”
The Kar Temp in my ’67 96 tells me that water freezes at 32 but it doesn’t specify units. It also says, however, that body temp is a little more than 98, so it certainly seems to be either °F or something so similar as to make little difference. At least it unambiguously identifies 0 as zero, which is comforting:
https://live.staticflickr.com/65535/52892377355_83ceb08ced_c.jpg
It is a wasted Microchip and programming. VW and apparently Kia both should focus that energy on something else. How did we ever survive the 100 years prior without this warning?
Survivorship bias?
Apparently my car doesn’t when other trims do. I guess the code for that got replaced by the code for the actual coolant temperature. A fine tradeoff IMO.
On my MK7 VWs it was just a loud chime – like you’d get with an imminent catastrophe like a red CEL – and a picture of a snowflake, but no text explaining what it meant or what to do about it.
They’ve gone backwards then. My Polo does the warning chime, but then displays the temperature, giving you a good hint of what it’s on about.
Yep that’s what my MKV/MKVI VWs have done as well, a chime and then the temperature flashes on the MFD.
Yeah VW is all over the place with this. My B6 Passat chimed, flashed the temp, and had the snowflake, I believe my MKV GTI did as well. My current Q3 chimes and put up the snowflake. We haven’t owned the ’22 GLI long enough to see cold temps to know what it does.
Now this is a cold start
Ha! I love that you wrote about this. I was a california resident and had an e91 BMW. Went on a yearlong assignment in London and was given an e90 to drive. First time I heard it on a chilly morning, I spent my commute puzzled. Nw I have a GX for snow trips into the Sierras and it chimes at 37 too.
Temperature variances are common. There is one section of my neighborhood park that can be 5-10° hotter or colder than the rest of the park. My guess is the wind swirls oddly due to geography and creates an isolated pocket.
Back when I bicycle commuted, I would frequently ride through hot or cold pockets of air. Especially when near streams.
Riding with hot pockets is highly recommended. They make for a handy snack after a couple of hours in the saddle.
Or Tots…
This has been a record spring for me, so far I’ve witnessed 3 people wipe their motorcycles out on cold pavement. Most years it’s only one or two. I guess they just don’t teach that stuff in riding school.
I assumed it was because most summer tires turn into marbles at 40°.
I assumed this would turn into a tire chemistry article.
Left disappointed.
My girlfriend is French and changed the language in her Fiat to French. So all these warnings show up in a foreign language on the rare occasions where I drive her car. This has made me really appreciate iconography in warning designs. My 500 day Duolingo streak has not included vocabulary about road conditions.
Hé, toé, c’est glissant dehors, calice!
Glizzys ahead! Where’s the hot dog stand? Damn, that owl has failed me yet again…
“Le grenouille mange la pamplemousse!”
Damn, I thought that light was telling me to turn on the air conditioner! It didn’t make sense; I mean, it’d be snowing and the stupid car wanted the AC turned on? I just figured, you know, robot overlords and all. Hang on a second, my nav system is telling me to turn into the ocean …
Cease to resist, giving my goodbye
Drive my car into the ocean
You’ll think I’m dead, but I sail away
On a wave of mutilation…
Wait, what warning light/chime? I have never seen this in any car.
I’m there with you. I’ve owned 5 cars built after 2000, live in an area where it gets below zero, and have never seen any warning like this.
yeah same, my Veloster doesn’t have this!
The bongs are super annoying. The first time I got one I thought something was actually wrong with my car but no, it was just telling me that it might be slippery. Thanks car, I can see the snow.
They are, and they sometimes come on at random times, like 15 minutes after leaving the driveway (the temperature reading is the same as it was when I first got into the car, why are you giving me this now?), and, since there is a temperature reading that’s clearly displayed at all times, the warning seems unnecessary, we already know how cold it is
My favorite thing is when I’m in a stressful driving situation and my car starts maniacally warning me that I am, in fact, in a stressful driving situation! Classic example: driving in icy conditions, backend of the car starts to fishtail, car is SCREECHING at me that we have lost traction. Thank you, car! I am aware!
Or, car in front stops, I apply brakes to stop, and “forward collision warning” comes up – thanks, got it, the guy’s over 100 feet away and I’m going 25mph, but the thing doesn’t make so much as a peep when a deer jumps into the road in the middle of the night and requires an actual panic stop.
I had a rental Nissan Sentra for about a week and one day on the drive home it jammed the brakes for about 2 seconds and scared the shit out of me. I don’t know what the automatic emergency braking saw in front of me but I was on a dead straight road with no other cars.
I really wonder if any of them work right, have not been impressed with Hyundai, Ford, or Toyota’s. Would prefer to not have it at all
Jason Torchinsky bringing us the cold, hard facts!
The coldest month of the year? Come over to Memphis. We’re in the 90’s already.
Now, only if there was a chime for shitty drivers up here in Montana in wintery weather. Or tourists in general.
Hold up — people really didn’t know this?
I have never seen or heard of this. I have never been in a car that had this, and I live in the northeast.
Nope, not one of our cars display this warning. I have a 2015 Infiniti Fx35, a 2015 4runner Limited and a 2017 Ford Flex Limited and I have never seen this warning.
As a South Florida Native, No.
The coldest day of the year here, might hit the high 40s lmao
Besides Kia, what cars actually chime when this warning comes on? I’ve never experienced one.
Visual warning, yes. Audio, generally no, unless dealers in cold states shut off the warnings before the cars are sold (which would be nice).
I rented a Jetta a couple of weeks ago, it had a chime for the freeze warning.
my last three are the only cars i’ve had with the warning, and all had audial and visual alerts: 06 mini, 13 fiat, 20 vw.
Toyota, Honda, and Kia are the brands I have had an audio alert in. I would prefer not to have it, but it’s there. Kia’s is the most intrusive. I don’t remember if my Civic was able to turn it off, but it seemed gentlest and quietest.
Interesting, none of the Toyotas I’ve owned have had it (or it’s been silenced somehow).
In general what I’ve seen:
Toyota and GM – visual warning, no audio.
Ford and FCA – no warning of any kind.
The German cars I’ve owned must have been too old to have this warning.
My BMW’s as old as MY 95 had this warning.
My 2001 Audi A4 and S4 both yelled at you. 1999 beetle too. 2007 Q7 as well.
I had a B5 Audi A4 a few years ago that would play the same jarring BEEP for everything from low windscreen washer fluid,or low outside temperature, all the way through to actual worrying things like low oil level.
Information overload like that is generally a bad design choice, I find.
It was a very stern German BEEP!!!
My MINI chimes. I think my Volvo also chimes. My Infiniti didn’t, but it was an ’03. Or maybe bridges just don’t freeze in Japan? Maybe Godzilla, Gamara, and Rodan keep them warm as part of the Tokyo-Kaiju Peace Treaty?
My ’06 VW Polo does. Just a bong and the MFD changes to the temperature.
Newer Subarus and Sprinter vans chime and display a snowflake at 37 F. My low-spec Kia has no visual or audio low temperature warning. My TJ’s low-temp warning is a cold draft.
All the German brands.
My Volt does. It’s somewhere between annoying and endearing in its attempts to safeguard the poor dumb meatbag behind the wheel.
And not just bridges! At night, water on the road can also freeze at air temperatures above 32 degrees due to the magic of radiative heat transfer: every sky-facing surface on the planet is radiating heat into the vacuum of space.
As long as outer space is colder than ambient air temperatures, which *checks physics notes* yep it usually is, you can cool things below ambient air temperature. Humans have been building refrigerators since long before the discovery of thermodynamics, much less electricity, based on this principle.
Yep. This is exactly why astronomical telescopes need dew heaters for the optics.
For all practical purposes, the scopes are always pointed at absolute zero.
I get what you’re saying in terms of their internal components but just to be annoying I’ll point out that their practical purpose as astronomical telescopes depends entirely on the fact that they’re NOT pointed at absolute zero.
I would be interested to know if this effect can cause water to freeze at 37 degrees. I suspect not, but if that were the case it would be a much better answer than the ones in the article.