Hi Dave,
You will not regret making the move to boat in the PNW area. It offers some of the most beautiful and varied boating opportunities that you could find anywhere (however, not tropical).
As others have stated, with some compromises, you can boat all year around. However, in the winter, late fall, and early spring, we usually have wet, cold weather. Not cold strictly in the temperature sense, but in the "how it feels" sense. Cool and damp means cold feel (sometimes to the bone). Most boats in this area have good heating systems, often diesel fired. However, a boat "lived on" in the winter up here can often suffer from condensation (dampness) issues, if not dealt with properly. The days can be dark and wet (lots of rain) in the winter and early shoulder seasons. However, as a bonus though, there are not many boats out, so you can have your pick of spots. We experience more and more severe winds in the winter and shoulder seasons, so that must be dealt with as well.
Personally, I get enough boating in the summer and my wife and I usually (not this year due to Covid issues (and family)) go out for 3-4 months straight and put on about 200 plus hours on average. I do go overboard and "winterize" the boat, but could get underway with a day or so's work if we decided to go out in the winter. We have done it in the past, but did not enjoy the winter boating experience "all that much". But, each to his/her own.
There is literally thousands of miles of explorable coastline in BC, Washington, and Alaska to visit with some of the most beautiful scenery in the world, and the summer, late spring, and early fall are mostly good weather for boating. Much of that coastline experiences little boating traffic at any one time, so if solitude is your thing, even in summer it can be achieved on BC's mid to northern coast, in Alaska, and on Vancouver Island's west coast.