Depends on "where" you live in the greater Seattle area. The term micro-climates gets used a lot in this area. Where Seattle rarely gets much snow, you can go 25 miles north or east into the foothills and it can change from 40 and a cold rain to 32 and snow...
Because of where I live, I got with a performance winter (Blizzak LM60) from December - mid-March. Then run summers the rest of the year. The summers (PSS) are fine in the rain...as long as it stays above 40. But, I don't want to risk it where I live. If I lived in downtown Seattle, I would be tempted to just use a summer tire year round...but not where I live and commute to.