What is Chicago’s lowest temperature ever recorded without any snow cover?

Dear Tom,

What is Chicago’s lowest temperature ever recorded without any snow cover?

Thanks,
Harold G.
Mundelein

Dear Harold,

Snow is a very effective reflecting surface and a prime factor in generating and sustaining winter’s extreme cold. Under ideal radiation conditions of clear skies and light winds nighttime temperatures can be as 20 degrees or more lower over snow cover than over bare ground. That being said, Chicago has logged subzero temperatures without a snow cover. Chicago weather historian Frank Wachowski found numerous examples with the lowest being 8 below zero on December 14, 1985. Other occurrences included minus 1 on an “unwhite” Christmas in 1990 and 7 below on February 18, 2006. The city’s most recent episode was a low of minus 4 on January 18, 2016.