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‘Wind chill’ system, adjusted in 2001, dates back to 1945

Patty Murray, Wisconsin Public Radio

The wind chill index, about which we'll be hearing at least through today, was developed in 1945 but modified in 2001. The change “toned down” drastic below-zero temperatures from decades past.

One thing is for sure: it's cold. But the recalibration of the wind chill factor makes it tricky to compare current conditions to those from a few decades back.

John Martin is a professor of Atmospheric and Oceanic Sciences at UW Madison. He says the wind chill basically centers on air temperature and wind speeds at the surface level. Higher winds make for lower wind chills. The formula was recalibrated a few years ago, however, to more accurately reflect a “feels like” temperature.

“The values now, the corresponding temperatures and wind speed gives warmer wind chill temperatures than the old scale,” Martin said. “So that scale has been revised to make it a little bit more difficult to get to the minus 35, minus 45 range as we did today.”

Either way, this winter is Wisconsin's coldest on record since 1996. Martin says the coldest recorded temperatures in Wisconsin date back to the early 1950s.

Sunday night's playoff game between Green Bay and San Francisco was likened to the famous 1967 “Ice Bowl.” But Martin says no records were broken, temperature-wise. “Although the Ice Bowl is remembered as being ... 20 degrees below zero, that was the wind chill, actually. The actual temperature at game time was one degree above, Fahrenheit,” Martin said. “I think it ended up being a little bit below zero by the end. [The 'Ice Bowl'] was windy, so it was miserable, but not as miserable as yesterday because we won then.”

Martin says Green Bay's low temperature during game time was four degrees above zero. The wind chill was estimated at 11 degrees below.