Our first substantial snowfall of the season visited Madison on Friday morning as a period of moderate to heavy snow fell from around 7 to 9:45 a.m.
In the end, we accumulated 4.4 inches of heavy wet snow timed perfectly to snarl the morning commute.
Friday’s event was just the fourth snowfall of 4 inches or more since the COVID-19 pandemic started in 2020. We wondered how often a cold season is visited by a storm with that much snow.
Using records from Dane County Airport as well as the prior site of the Madison airport, it turns out that 209 such snowfalls have occurred since 1939 — 75 of them since 2000. Interestingly, 20 of the last 83 winters have had only one 4-inch or greater snowfall, and seven others have passed without a single event of that magnitude.
That means that just shy of one-third of the time, a winter season in Madison comes along in which, at most, only one snowfall of 4 inches or more occurs.
That may seem hard to believe given that our seasonal snowfall averages 50 inches each year. However, the majority of a seasonal snow total in Madison is often made up of a series of quite small amounts.
Though the average number of days on which at least 1 inch of snow accumulation occurs in Madison varies enormously from year to year, the long-term average over the same interval has increased from roughly 12 days each winter to about 15. The record is 27 such days in 2007-08 — when we set the all-time seasonal snowfall record of 101.4 inches — while the record minimum number is just 2 in 1967-68.
Thus, it is hard to tell whether what we experienced on Friday morning will be a common occurrence this winter.
Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at email@example.com or firstname.lastname@example.org.