What is the average date for Chicago’s first sticking snow of the season?

Dear Tom,
Can you shed light on the average date that Chicago has had its first sticking snow of the season? It seems later in recent years, and is this due to climate change?
— John Holden, Edgewater
Dear John,
Chicago’s snowfall records go back to the autumn of 1884 (134 years of data). The average date of the first measurable snow (0.1 inch) of the winter season is Nov. 16 in those 134 years. However, in recent years, as you have noted, the season’s first measurable snow has occurred later.
Since 2001, the average date has slipped six days to Nov. 22, and that is despite this season’s first measurable snow (a mere 0.1 inch) on Nov. 10. In seven of the 17 years (2001-17), the first measurable snow occurred in December. Whether this is due to climate change is a matter of debate due to the small sample size, but it certainly does reflect a pronounced trend.