November 10, 2014
The Wind Chill Myth
A cold wind can chill you to the bone, no doubt. But what does "wind chill" really mean, and is it even an accurate concept? The real answer might surprise you.
You hear about wind chill all the time once temperatures start to drop. It's one of those things people love to throw out when discussing the weather: "Did you hear? Its 10 degrees out, but with the wind chill its 15 below zero!" It's become so commonplace, many people disregard the actual temperature and go straight for the wind-chilled "effective" temperature – because it just sounds so much more interesting.
As a rider, wind chill is something you're even more keenly aware of. We've all been chilled to the bone on a ride when it's only moderately cold out, because of the blast of "wind" created by rushing through air on a bike at high speed. What would be slightly chilly standing still suddenly feels like a polar vortex when riding down the highway.
I know riding a motorcycle at speed magnifies the cold, because I've felt it. But when I set out to understand wind chill as a scientific model, I was surprised to find out that it's actually not very scientific at all. It turns out that "wind chill" is really a very hazy concept, rooted in some very inconsistent assumptions, and it's probably one of the most subjective and misused measurements in all of weather science.
Why Does Wind Make You Cold?
Wind doesn't actually reduce temperature at all – all things being equal, it is impossible for wind to reduce the temperature of something below the ambient temperature.* Any non-living object can only be chilled to the ambient temperature, and not below it. The temperature isn't actually causing the temperature to drop; it only feels like it is to humans, because of the body's physical response to cold. By constantly blowing away the heat the body generates, convection (the transfer of heat by flowing air) creates the sensation of being colder than it actually is.
*I said "all things being equal" because this doesn't account for the effect of moisture and evaporation. If something is wet, and wind is passing over it, the evaporative effect can drop the actual temperature of the object. When you get out of a pool on a hot day, and a breeze hits you and makes you feel cold, this is technically not "wind chill" but rather evaporation.
How is Wind Chill Calculated?
Because wind chill tries to measure the perception of cold, and not the actual temperature, it is necessarily an inexact science (and one might say, not actually science at all, since it is not consistent or reproducible.) Different people in varying conditions will feel different at varying levels of cold. Wind chill is in fact only an approximation of a feeling - and a very rough one at that.
The problem is that, unlike temperature – which is a uniform and exact measurement – there is no universally accepted standard for the effects of wind chill. Different countries actually use different formulas to estimate wind chill, and they have changed significantly over time (In Europe, "wind chill" isn't even a commonly used term - check out this headline from last year in BBC News entitled "Who, What, Why: What Is Wind Chill Factor?") The current standard for measuring wind chill was developed only recently, in 2001, and it's based upon the estimated effect of wind on a bare human face walking into the wind at 3mph.
In addition, because wind chill is calculated as the feeling of cold wind upon bare skin, the degree of wind chill estimated by the formula would only apply if you were completely unprotected by windshields or fairings, and if you weren't wearing any clothes. Hopefully you don't ride like that (but if you do, we don't want to know!)
So ultimately, wind chill is only an attempt by science to describe the sensation of cold on the skin as it is affected by wind. It's not an actual unit of measurement, and it varies from person to person depending on their tolerance to cold, what they are wearing, and even the level of moisture in the air.
Does That Mean Wind Chill Doesn't Exist?
Heck no! Anyone who's ridden a motorcycle in the cold can tell you that zooming through the air makes it feel a lot colder than it is. But that's just the thing – it's all about feel, and everyone feels cold differently (personally, I'm a pretty big wimp when it comes to the cold.)
My point is not that it doesn't exist. Only that it's far from exact, and based on the way it's measured, is usually grossly exaggerated. Wind-chill reports tend to exaggerate the actual rate at which you feel cold, and those reports often end up being discounted by most people who have experience in cold weather because it does not tend to agree with personal experience.
How to Fight Off Wind Chill on a Motorcycle
Since riding a motorcycle doesn't usually involve much physical activity, your body isn't doing much to generate its own heat. This means you have to do all you can to insulate the heat you do have, to prevent it from being whisked away by rushing air. If you protect yourself from the cold adequately with windproof warming layers and even heated gear, you can take huge steps toward making wind chill become almost not a factor at all.
Fighting wind chill comes down to two components: insulation layers to slow the rate at which body heat is lost, and wind proofing to prevent rushing air from stealing that heat away.
Layering is critical to all cold-weather activities, including motorcycle riding. Good bottom layers are things like a snug fitting poly fleece or wool, followed by down or synthetic down insulating layers. Heated gear is also highly recommended for motorcycling since you have a power source - your bike - available to you. (Check out our complete buyers guide on heated gear by clicking the banner below.)
Wind proofing is where you seal the heat in to keep it from being stolen away by the rushing air. The most important part of wind proofing is seamlessness – all the money you spend on high end windproof gear doesn't mean squat if you have weak points where all the heat is escaping. At motorcycle riding speeds, that small gap between your gloves and jacket cuffs or between your collar and helmet suddenly become gaping holes in your cold defenses. And you won't just have a cold neck or wrists either; because blood is being pumped throughout your circulatiodn system constantly, those small cold areas literally spread cold throughout your entire body!
On a motorcycle, its critical to be able to seal up those leaks with Velcro, drawstrings, and even versatile items like a scarf or balaclava. And don't forget the single biggest wind protection item you can use, and you don't even have to wear it – a windshield!
To help you calculate the degree of protection you'll need on a ride, we created this wind chill chart for motorcycle riders, with wind chill factor expressed at common cruising speeds.
What Is The Coldest Wind Chill Ever Recorded?
According to WikiAnswers, the coldest wind chill ever recorded on earth was -192 degrees Fahrenheit at a remote weather station in Vostok, Antarctica in 2005. The high temperature that day was -99 degrees, and wind gusts reached up to 113 MPH, resulting in the -192 degree wind chill. Try riding a motorcycle in that!
What do you think about wind chill? Do you think wind chill is exaggerated, or is it totally legitimate? Let us know in the comments below!