Temperatures after the 1967 blizzard

Dear Tom,
After the 1967 blizzard, Chicago temperatures held pretty much in the 20s and 30s. Was it rare for the temperature not to fall below zero after such a big snowfall?
—David, Chicago
Dear David,
You are correct that no subzero weather followed the city’s benchmark 23-inch snowstorm Jan. 26-27, 1967. The lowest reading through the end of the month was just 15 degrees. Longtime Chicago residents are well aware that subzero weather often follows major snowstorms, especially from mid-December through mid-February, because the storms often develop along a frontal boundary ahead of an arctic air mass. Following the “Big Snow” the southern extension of the arctic air was pinched off, with the bulk of it spreading to New England and Quebec, while Chicago remained in a return flow of Atlantic air circulating around the departing storm.