Dear Tom,
What are the parameters used to calculate the total snowfall for the winter season?

Richard Jones, Elgin

Dear Richard,
A running sum is kept of the snowfalls from the first trace of snow in the fall to the last trace in spring and the final sum is the total snowfall for the season. Chicago’s snowfall climatology dates back to the winter of 1884-85, and over the course of those 137 snowfall seasons, the seasonal snowfall extremes range from a low of 9.8 inches in the winter of 1920-21 to a maximum of 89.7 inches in the winter of 1978-79. The city’s normal seasonal snowfall is determined on a smoothed 30-year period, and currently stands at 36.3 inches based on data from 1981-2010. By early next year, that 30-year normal will be recalculated, based on the 30-year period from 1991-2020.