I lived in Seattle for twenty years. We got significant snow/ice three times. Once, just enough for the buses to slide down the hills (in fairness, everything was sliding, but you notice a 70 foot articulated bus more than an Escort), once a quarter inch of ice on everything (here's me standing in the freezing rain at midnight, chipping it off the car that I had the forethought to park where I could actually leave, instead of in the underground garage), and once a foot on Monday, another foot on Tuesday, and then a couple inches of rain on Thursday (followed by literally hundreds of roof collapses).
On that basis, I'm going to call this once in a decade, give or take...