This past month felt cold; in Virden over the last half of January we averaged around -22°C, eight degrees below normal for this time of year. So right there we are off to a poor start; add in some breezy conditions and you have the recipe for wind chill and the misuse of the phrase.
The temperature on the thermometer is the temperature, that is how cold it is, wind chill does not make the air temperature colder. If the temperature is 2°C with a 20km/h wind it should “feel” like -3, however that would not freeze water, so therefore it does not lower air temperature.
Inanimate objects such as vehicles, buildings, etc. do not experience wind chill. No matter how hard the wind is blowing, they experience the air temperature. It is impossible to cool these objects below the air temperature.
It may be hard to believe but when you are driving down the highway travelling 100 km/h at -30°C the front of your vehicle is experiencing -30°C not -54°C.
Humans and animals on the other hand feel the effects of the wind and thus we try to represent this in a value that we feel.
Wind chill is a calculated guess at what a human might feel as a result of the wind; it is not actually measurable and not a temperature. Wind chill is unitless, you can not attach a °C to it.
Different countries around the world use different formulas for calculating the wind chill. Even in Canada we have changed how we calculate and represent this value.
Up until 2001, wind chill was expressed in watts/m² and assigned a value from 900 to 2600 - pretty useless right?
After 2001, a number was assigned to those values that would more closely represent what a person would expect to feel. There are many assumptions built into the wind chill formula. Some of these assumptions are that your exposed face is roughly five feet off the ground, it's night, and you're walking directly into the wind in an open field at a speed of about five kph.
Wind chill is not useless; it does give the public a best guess at what you would feel under certain conditions. We must be careful how we use it and what we are trying to convey when we put the value to use.
Meteorologist Riley Hole owns and operates Prairie Weather Services out of Virden.
