This is the newer chart that was revised a few years back, I'm not sure what exactly they based their revisions on but I know the revision made the feels like temperature a lot less dramatic, I think it nearly cut the wind chill temp in half, what they used to chart as -40 is now only considered -20. So when some old timer is telling you a story about how he was walking to school up hill both ways in -50 degree wind chill temps, you can tell him that it really wasn't -50.
I found the old chart, it definitely read the temp as a lot colder than the new chart!
