I love answering viewer questions. This morning I got a good one!
"It says 7 degrees feels like 3. How can that be? If it feels like 3, surely then it is 3 degrees?”
Well, yes and no. The “feels like” temperature refers to the wind chill.
What is wind chill?
Wind chill is a value forecasters use to express how much colder the wind makes the air feel on unprotected skin. So, why don’t we just say that it’s 3°C if that’s what it feels like? Well, the wind doesn’t actually change the temperature of the air which is why, in our viewer’s case, the thermometer still reads 7°C.
What the wind does do is blow away the warm layer of air that surrounds our skin, exposing us to the elements. It takes a lot of energy for the body create another layer of warmth. If it keeps getting blown away by the wind, our skin temperature will drop and we will perceive conditions to be colder than they actually are. Another factor is moisture. Wind will draw heat away from the body through evaporation.
How is wind chill calculated?
Here’s the formula Environment Canada uses to determine how skin temperature changes as wind conditions and air temperatures change:
Where Twc is the wind chill index, based on the Celsius temperature scale; Ta is the air temperature in degrees Celsius; and v is the wind speed at 10 m (33 ft) standard anemometer height, in kilometres per hour.
Before you ask, yes, in school I had to solve for Twc by hand without a calculator. You don’t have to, though. Thanks to the brilliant folks at Environment Canada, there’s a wind chill calculator online.
Give it a try. Plug in your temperature and the wind speed and see if your current conditions feel dramatically colder than they actually are. Note: the wind chill calculator is only valid for temperatures up to 5°C, as it’s primarily used during colder weather.
Weekend weather look-ahead
We’ve endured a number of spring storms this week that had us all keeping an eye on the winds. Today they peaked at 70 km/h around the Comox area.
And then there was plenty of rain. The School Based Weather Station Network illustrates today’s rainfall perfectly. Here’s how much rain has fallen since midnight
Good news. The weekend, while still unsettled, starts to show some improvement.
There will be sunny breaks and showers will become less frequent. I can hear the symphony of lawnmowers already.
