A Wind Chill Primer

by Arthur Milner

If you’re old enough, you might remember that about 30 years ago weather forecasters started trying to scare you. I believe it coincided with the arrival of “the weather channel.”

Weather forecasters’ first weapon was to err on the side of “bad.” You might have noticed that it’s almost never as cold as predicted, and there’s almost never as much snow or rain as predicted.

But apparently simple exaggeration didn’t scare us sufficiently, so they invented humidex and wind chill. Now numbers could be far higher and lower and, therefore, far more frightening.

It’s winter, so I’ll focus on wind chill. There are two things to keep in mind. First, there’s no such thing as wind chill. “The temperature is -7°C, but it feels like -27.” Feels like? Now there’s science. Why not say it feels like -12 or -30? Oh, I know. We’ll measure it. But you can’t. There’s no such thing as a windchillometer. What they do is, take the temperature, multiply it by the wind speed and some other magic number and — voilà!: you have wind chill. A number high enough to scare parents, increase business for cabs and Uber, and to get you to keep the radio on ‘cause any moment there might be a WEATHER WARNING!

Second, and I’ve been told this by actual weather people (the rest of this I figured out or made up, as you prefer): they fudge the numbers. They start with the forecast temperature, for which they are already erring on the side of the bad. And when they factor in wind speed, they use “maximum gust speed” (my own neologism), the wind speed at its highest that day. If the wind speed is forecast to be 5km/hr with gusts up 15km/hr, guess which number they use?

It’s a little complicated, but here’s the math. Let’s say that — just to be safe — you’ve reduced the forecast temperature by 3°C. And by using “maximum gust speed” instead of average wind speed, you reduce the temperature by °6. If you add the two, you get a difference of 9°. But if you multiply them, you get a whole 18°!  What will they think of next?

Why are weather forecasters and the media — especially radio stations, I would say — trying to convince us that the weather is trying to kill us? I suspect it’s that old cliché about the media: “If it bleeds, it leads.” It’s the same reason there’s more crime reporting. It gets our attention. There’s no more crime than there used to be; and, if anything, winters are getting warmer.

So, if it’s going to be -7°C tomorrow, bundle up. And if there’s a wind, wear gloves and a hat that covers your ears, because exposed skin will feel especially cold if it’s windy. But ignore the artificially scary numbers. Go outside and enjoy yourself.