How cold is it really?

A couple of weeks ago I was standing at my kitchen sink. It was morning and the sun was just starting to rise. The wind was tossing snow about in the street outside and buffeting the stove hood vent causing a racket. I said to my husband “I’m not excited to go outside today, it sure looks nasty”. Fast forward through breakfast, I pass him in the hallway. He is getting out his biggest coat and says to me: “it’s a parka day today.” I agree and suggest that today’s out-of-the-house appointments are not really all that important. It is the Christmas holidays after all. He heads out anyway to bravely face winter’s rage.

I bundle up tiny and wait by the door for his re-entry into warmth. But no cold accompanies his return to the house. “We were wrong”, he says, handing me his coat, “can you get me a sweater instead?” The temperature that day? A nasty -2OC. The language that we use to describe the weather matters. This is true when we are discussing the weather with friends. It is even more true when the source that we go to for impartial information is telling us that the weather ‘feels’ much colder than it really is. In the current news climate the mantra that ‘drama sells’ has made it’s way into weather reporting. Nowhere is this more apparent than the infamous wind chill factor.

The wind chill, reported as ‘feels like’ in its current iteration, is often ridiculed for its negative exaggeration of the current temperature. That’s because wind chill is not designed to represent the temperature at all. You may have noticed (although I didn’t until researching this) that Environment Canada does not include a degree sign behind their ‘feels like’ temperature. This is purposeful. The idea is that it will help people avoid thinking of wind chill as a measure of temperature. (It may just be me, but I think discarding the term ‘feels like’ would do an even better job of accomplishing this.)

If the wind chill index isn’t reporting temperature then what is it?

Wind is inherently intangible. If you will bear with me I would like to paint you a picture. It’s a warm summer day, you wade into a lake. It’s cold at first, but as you stand there admiring the view the water starts to feel warm. Just when you are starting to really enjoy yourself some jerk drives his boat too close to the swimming area and waves splash around you; the water surrounding you moves and you are suddenly cold again. We have all had this experience and we intuitively know that the sudden chill is the result of the water that our body heat has warmed moving away from us, forcing us to heat brand new water. What is less intuitive is that on a dry winter day your body is heating a thin layer of air around you. In the winter drama the wind plays the part of that jerk with a boat and you are left constantly trying to warm new air.

Regardless of the strength of the wind, objects (like your skin) will not be cooled below the ambient temperature of the air but they will cool more quickly (this explains why wind chill has no affect on your car). Wind chill attempts to quantify the contribution of wind to the speed at which the skin cools.

The current iteration of the wind chill index was developed by an international committee in 2001. It’s purpose is to give a rough idea of how long it will take for exposed skin to develop frost bite given the current temperature and wind; more specifically the skin on your face. (Well, maybe not your face). The development process included a study that recorded the changes in the skin temperature of volunteers walking in a cooled wind chamber. This number is then connected to the ambient temperature at which frost bite sets in over the same amount of time.

The very obvious problem with this endeavor is that the time-to-frostbite number depends on so much more than just the wind velocity and temperature. Each individual has a different capacity to withstand cold temperatures – impacted by many factors such as body type, conditioning, and activity level. In addition to personnel discrepancies the wind chill index fails to consider things like the amount of sunshine and humidity. (Side note: AccuWeather has a RealFeelR index that considers these factors. It seems to be closer to my personal ‘feels like’ temperature.)

Despite these flaws, my opinion is that the wind chill index (represented as amount of time before frost bite is likely) can prove valuable for the purpose of determining how long you can safely be outside. It is especially useful for people who would like to increase their winter activity and lack the personal experience necessary to make safe decisions or for those making decisions for large groups such as schools and day cares. You can find out what time-to-exposed-skin-frostbite the wind chill predicts by going to https://www.canada.ca/en/environment-climate-change/services/weather-health/wind-chill-cold-weather/wind-chill-index.html#X-2015011511225016 and selecting: wind chill hazards.

Problems compound when the wind chill index is used to create a pseudo-temperature. It has little to no value in this form. Combining ambient temperature and wind chill leads to a loss in valuable information. Preparing for a -34 deg day requires a different tactic than preparing for a -20 deg day with a 40 km/hr wind. On a windy day an experienced person might change their route to seek out treed areas sheltered from the wind. On a calm, cold day location is not as important, but long johns are. It is a misnomer to report both of these days as -34.

If wind chill isn’t the solution then what is?

Unfortunately there is no real shortcut; knowing how to dress and how to act outside requires experience. Luckily that experience is very easy to build, you just need to spend time outside in all weather. Before you start gaining that experience it is important to know the signs that you are getting too cold and what to do about them. (Scroll to the bottom of the page if you’d like to read the definitions and recommendations for hypothermia, frostbite and frostnip from Environment Canada).

For a lot of us the wind in km/hr is difficult to picture. The Beaufort Scale does an elegant job of expressing the wind speed in images, which connect much more easily to experiences. (I created a pretty copy of the scale. You can find the full Beaufort scale on the Royal Meteorological Society website https://www.rmets.org/resource/beaufort-scale.)

When I was a kid we listened to the weather when we wanted the forecast. But if we wanted to know how cold it was we used a combination of the thermometer hanging outside the window and the windsock in the field. It wasn’t exact, but it told us what we needed to know. If we ever asked my father how cold it was and if we needed to put on [long johns/ a big coat/ insert item here] he would say, “I don’t know, go out and check”. By which he meant: walk out onto the porch and you’ll know what to wear.

It annoyed me. I didn’t want to stand out in the cold in my pyjamas, I just wanted him to give me his advice. At the time I didn’t realize that was what he was doing. No one else can tell you how the weather is going to affect you. You need to decide for yourself. You can’t do that when your weather app is shouting at you ‘VERY COLD’. For the rest of the winter I will be providing drama-free weather. Ambient temperature, wind in Beaufort scale and precipitation. That’s it. (Ok, I may add in the odd recommendation for a day-appropriate outdoor activity. But that’s it.) No drama.

What do you think? How do you gauge the weather? Do you have any burning questions left about wind chill?

RESOURCES AND FURTHER READING

The following definitions and recommendations for hypothermia, frostbite and frostnip come directly from Environment Canada’s website:

Hypothermia: Being cold over a prolonged period of time can cause a drop in body temperature (below the normal 37ºC). Shivering, confusion and loss of muscular control (e.g., difficulty walking) can occur. Can progress to a life-threatening condition where shivering stops or the person loses consciousness. Cardiac arrest may occur. What to do: Get medical attention immediately. Lay the person down and avoid rough handling, particularly if the person is unconscious. Get the person indoors. Gently remove wet clothing. Warm the person gradually and slowly, using available sources of heat.

Frostnip: A mild form of frostbite, where only the skin freezes. Skin appears yellowish or white, but feels soft to the touch. Painful tingling or burning sensation. What to do: Do not rub or massage the area. Warm the area gradually – use body heat (a warm hand) or warm water. Avoid direct heat which can burn the skin. Once the affected area is warm, do not re-expose it to the cold.

Frostbite: A more severe condition, where both the skin and the underlying tissue (fat, muscle, bone) are frozen. Skin appears white and waxy and is hard to the touch. No sensation – the area is numb. What to do: Frostbite can be serious, and can result in amputation. Get medical help! Do not rub or massage the area. Do not warm the area until you can ensure it will stay warm. Warm the area gradually – use body heat, or warm water (40 to 42ºC). Avoid direct heat which can burn the skin.

The beaufort scale km hr.png

Henson, Robert. “Cold Rush.” Weatherwise 55, no. 1 (January 2002):

Hilton, Carol. “Gauging Wind Chill.” Canadian Geographic Vol. 121 Issue 5 (Sept/Oct 2001)

Horstmeyer, Steve. “Tilting at Wind Chills.” Weatherwise 48, no. 5 (October 1995):

“Wind Chill Index.” Government of Canada – Environment, June 2, 2018, accessed January 18, 2020.


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