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When the temperature drops, weather forecasts start to include wind chill.
It is a much-maligned term trotted out during our long and cold winters that folks either love or love to hate.
So let’s take a look at the most common myths.
There’s no such thing as wind chill
Because it’s not a measured atmospheric condition, wind chill can be divisive. Some hate the term and think it’s misleading, but the principle behind wind chill is very real, even if the value is a calculation not a measurement.
When it’s cold out, our bodies will warm up a thin layer of air next to our skin. If the wind picks up, that layer of air is removed and the air up against our skin is once again cooler. Your body will keep trying to warm up that layer of air, and the wind will keep removing it — which will cool you down faster.
Wind chill means it’s colder out
When you hear someone say “it’s minus 50 out!” they are probably talking about the wind chill and not the temperature. In Canada, parts of the north can get to -50 C, thanks to the high latitude, but in much of Alberta and Saskatchewan, even getting to a true -30 C is more rare than you might think.
Temperature is an atmospheric condition that is measured. You can go outside right now with a thermometer and get a temperature reading.
Wind chill is calculated using a given temperature and wind speed to give you that “feels like” value. In other words, it’s what the air feels like on your exposed skin.
It’s only -5 C, so I don’t need a hat
Speaking from experience, I would be careful with this one because frostbite is no fun.
If it’s calm, maybe that statement is true — depending on how long you’re outside. But if the wind is whipping, that’s when you run into trouble.
Wind chill is used in weather reports to show you the risk of frostbite on exposed skin. Depending on the wind chill, it takes a certain amount of time for your skin to freeze — the higher the wind chill, the faster you will get frostbite.
So if the wind chill is reported at -30, it will take anywhere from 10 to 30 minutes for your skin to freeze.
If it’s a really blustery and frigid day, and the wind chill is -50, you can get frostbite in just two to five minutes.
It’s important to look at the wind chill if you’re spending a lot of time outside because the results can be painful and even dangerous.
Extreme cold warnings ignore wind chill
When we are in the depths of winter and a cold air mass descends from the Arctic, the map of Canada is often painted red with warnings. But sometimes, instead of a solid block of warnings, it looks like a puzzle with pieces missing.
So why do you see an extreme cold warning for Toronto when the wind chill there is only -30, but in Alberta and Saskatchewan at a -30 wind chill, there is no warning in sight?
It’s because different areas of Canada have different criteria to hit before a warning is issued, depending on local climate normals.
In Alberta and southern Saskatchewan, you need a temperature or wind chill of -40 for at least two hours before you see a warning (that number drops to -45 in northern Saskatchewan).
You only need a wind chill or temperature of -30 in southwestern Ontario for a warning, but in much of Nunavut you would need to hit -55.
Wind chill doesn’t affect objects
This is actually false. Of course you don’t have to worry about your car getting frostbite so it may not be as relevant, but wind chill can affect inanimate objects that are warmer than the outside air. The effect is the rate of cooling.
On a windy day, we know our skin will cool down faster, and the same can be said for other objects.
It’s similar to when you blow on a hot cup of coffee to cool it down. The higher the wind chill, the faster things will cool to the ambient air temperature.
Now that being said, if it’s only -5 C but the wind chill is -20, do you need to plug your car in? No. Objects in a cold wind chill will not cool down below the air temperature.
If it’s -5 C and your car is sitting outside already at that temperature, the wind can blow all it wants; your car will still be -5 C.
Our planet is changing. So is our journalism. This story is part of a CBC News initiative entitled Our Changing Planet to show and explain the effects of climate change and what is being done about it.