Seattle climate: Pacific Marine. Around late September to early October, the switch flips and the High pressure ridge no longer holds. The sunny, temperate summer (July 4th–September 20th) is gone, Jack. A few bigger storms move in (more wind and relatively more rain). In come the clouds, and the drizzle, and because we’re at 48 degrees north latitude, the darkness.
As for snow, there’s plenty of moisture around, but getting the moisture AND the cold air together is tough. The cold air dams behind the Cascades and up high and in Eastern Washington. Sometimes it drains through the Fraser River valley and spills over Seattle. You might not get any snow for a winter or two, or you might get 1-2 weeks of below freezing temps, and 2-24 inches of snow on the ground before it melts with the next rain. Lots of variability.
Dress in layers with moisture protection. The difference between the rare sun on your skin and walking through a damp, chill fog could be 15-20 degrees. Expect low light, and sunrise as you go to work and sunset before you leave.
Join a club…and get some good exercise. Wait for late April or May to start seeing real sunny days again.