Either your memory is especially impressionistic, or you ought to consider an appointment with a gerontologist. I couldn’t find hard data, but I am reasonably certain that the Chicago Public Schools average at least 1 snow day per year, not 1/30th. Even the University of Chicago – which prides itself on never having snow days, because so much of the faculty and administration (and of course students) lives within walking distance – has had to cancel classes at least a couple of times in the past decade.