A New Wind Chill Chart
It has been said that the only thing
constant in this world is change, and now even the familiar old wind chill chart
has been revamped. The old formula for the chart was derived in the 1940s by a method
that noted the length of time required for a bottle of water to freeze under a variety
of wind speeds and air temperatures. Since little was known about the thermal transfer
properties of skin at the time, the chosen plastic container skewed the results.
The old chart yielded a wind chill factor that was too low - by tens of degrees
Fahrenheit in extreme cases. Using modern methods that involve bringing the skin
of human volunteers to near freezing, a new formula - and new chart - was born in
the year 2000. An example: A 20 °F day with 10 mph wind, now has a wind-chill rating
of 9 °F instead of 3 °F.