"Snow" in general is a little bit of a weather red-herring; most cold-season flight delays that I've encountered have been attributable to other forms of frozen precipitation. Light to moderate steady snowfall that accumulates at middling rates rarely causes flight delays in airports accustomed to dealing with it (e.g., northern Canada); conversely, I've spent many hours on the tarmac waiting for deicing (and snow removal) equipment at American airports . And freezing rain/sleet is the worst of all -- I've skipped flights because of it. I can only think of two times in my flying history that my flights were delayed because of heavy snow alone-- and both of those were out of BUF.