## Tech, Autos, & Gear in Layman's Terms Since 2006

December 10, 2013 • Gear Bits

# Sorry Apple Weather, That Is NOT How You Calculate Wind Chill

Wind Chill Factor

When I was a kid, the concept of ‘wind chill’ was new; the National Weather Service didn’t start reporting it until the 1970s, and it took a while longer to become popular with news viewers. Now it has evolved into ‘Real Feel’ or ‘Feels Like’ rather than just ‘Wind Chill’. Either way, Apple’s Weather app doesn’t have a clue.

As you see above, the temperature when I grabbed this screen was 30F. The next screen shows the wind and the ‘Feels Like’ temperature – and although the wind speed is 16 MPH, the temperature apparently shows no impact.

Of course, if you know anything about being in a cold wind, you know that 16 MPH winds have a VERY significant impact on how things feel! Here is the calculation used by the National Weather Service, with T as temperature and V as wind velocity:

Wind Chill = 35.74 + 0.6215T – 35.75(V^0.16) + 0.4275T(V^0.16)

Based on that calculation, 30F with a 16 MPH wind feels like 19F. Which is about right. Here is the full NWS graph:

It is funny, because I noticed this effect before, and in particular as we had a fire alarm at my work yesterday afternoon – the temperature was 39F and everyone was remarking how warm it was … until we had stood in the parking lot for 20 minutes with 22 MPH winds (Wind Chill 22F, or according to Apple … 39F).

But seeing the post from Carly brought it back to my mind, and as I stopped by the market earlier I was blasted by the wind and decided to check … and this is what I found.

So if you are trying to check for wind chill – don’t trust the Apple Weather app!