SIOUX FALLS, S.D. (KELO) — The concept of wind chill has been around since 1945, but over the years, it’s gone through a bit of a change.

KELOLAND’s Jay Trobec explains.

“The wind chill index was invented in 1945 by arctic explorer Paul Siple, who wanted to measure how winds magnify the effect of cold air on bare skin,” Trobec said. “His formula was used by the National Weather Service for many years.”

Records regarding wind chill are not formally kept, according to Trobec, but the National Weather Service (NWS) has kept some data.

“The lowest wind chill they could find was at 1:00 a.m. on Christmas Eve in 1983. It worked out to a wind chill of –80 in Sioux Falls, using the ‘old’ wind chill formula,” Trobec said.

Another extremely cold day came in 1995. Trobec remembers the experience. “I recall the wind blowing so hard that the propeller of the plane behind me was spinning, even though it wasn’t running,” he said. “I can still feel a tingle on the back of my ears from the light frostbite I suffered while doing that report. But I am certain that it didn’t ‘feel like’ what –65° would.”

Researchers in the U.S. and Canada felt Siple’s formula overestimated the wind’s effect, so they set out to correct it.

“They put sensors on volunteers on a treadmill in a wind tunnel to quantify wind chill on the face of a five foot tall person walking into a 3 mph wind,” explained Trobec. “Converted to a math formula, the result was the wind chill index chart created in 2001 and that we use today. It makes “feels like” wind chill values more realistic.”

Using this new and improved scale, Trobec points out that the “coldest day” back in 1983 did not quite feel like -80 — rather, it was closer to -57.

Positively balmy.