Dear Tom,

How does the new wind chill factor compare to the one used years ago? In the winter of 1983 or 1984, my brother and I walked to Mother’s Pinball in Mount Prospect when the wind chill was lower than minus 80.

Mark Cassiere Sleepy Hollow

Dear Mark,

The Chicago winters from the late 1970s to the middle 1980s were very cold and snowy and produced some of Chicago’s most extreme winter weather. On several occasions, the mercury tumbled below minus 20 and was accompanied by very strong winds. There were many occurrences of wind chills lower than minus 60 with the city’s all-time lowest wind chill computed at minus 82 on a frigid Christmas Eve in 1983 with a high of 11 below and a low of 25 below zero. By 2000, it was determined that those wind chills were unrealistically low and in late 2001 a new “milder” wind chill calculation was instituted in the United States and Canada. The formula was revised because most wind equipment measures the wind speed at 10 meters, about 33 feet above the ground, but the winds at a typical human height (5 or 6 feet) are seldom as strong. The new measurements were clinically tested and shown to provide more realistic wind chill values. The minus 82 Christmas Eve wind chill now computes to about minus 58.