Its like this: when you have arctic conditions (like since Christmas, or, February 2015) the snow stays pretty clean even in the cities. You adjust to the cold and really start getting out in it, snowshoe, ski, etc. Then, temps rise to 30F and everything starts to get nasty. So, "normal" winter weather in SNE helps out by providing a cleansing rain to wash away the dirty stuff until the next good snowfall comes. This is not a historic event; its should not be a hysteric even either.
I'd keep the arctic cold (minus the wind) and the clean snow pack if I could. But if I can't, then a little clean up before the next event isn't such a bad thing.