Wind chill: It’s not the same as it used to be…

Many people remember the big events from years ago and forget all of the “normal” weather days, which leads them to remember that was “always” this way or that. In fact, most people remember weather events from one day in one year and attach it to an entire generation’s worth of weather. I’ve had people tell me that they can remember snow up to their roof-line “all the time when I was young”, but the more you pry it turns out to have only occurred once in a blizzard. The vivid memory can skew your thinking and give you a false sense of what the weather was really like over a long period of time.

Having said that, there is one area that your memory might not be playing tricks on you. Do you remember the days of -40°F to -50°F wind chills in Kansas? Do you ever wonder why we don’t have those now? And why it seems the mention of -20°F is a bigger deal now than it used to be? Well, there is a reason for that. It all goes back to November 2001 and a change in the formula that didn’t seem to get stored away in people’s memories, so here’s a refresher on it.

Prior to November 2001, to compute the wind chill we used the formula:

Old Wind Chill = 0.0817(3.71V^(0.5) + 5.81 -0.25V)(T – 91.4) + 91.4, where T is the temperature in °F and V is the wind speed in miles per hour.

old wind chill chart
Wind chill chart used prior to November 2001.

 

Fast forward to today and we used an updated wind chill that gives more accurate representations of what effect the wind really has on your body. It is:

New Wind Chill = 35.74 + 0.6215T – 35.75V^(0.16) + 0.4275TV^(0.16), where T is the temperature in °F and V is the wind speed in miles per hour.

Wind chill chart used today.
Wind chill chart used today.

You can clearly see the difference, right? Probably not, but the end result is quite a bit different and most often will give us a “warmer” wind chill now than it used to. Hopefully, it is now far more accurate and can be applied more easily. The problem is that we can never compare a wind chill in 2015 to a wind chill in 1975 or any other time before the switch was made.

Here are a couple examples of how things have changed.

Old Wind Chills vs New

So while the wind chill may not be as shockingly low as it used to be given, cold air and cold wind are still just the same and can be just as dangerous as ever.

– Storm Track Chief Meteorologist Matt Miller

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