I'm also in the NW so I found out when I bought my RV that we had to book way in advance if we wanted a weekend spot. If you are looking for weekday, they are usually a little easier. I booked our July spot in November and our August spot by December, but that one is in MT. We tried to book a memorial day weekend back in November, but couldn't find an opening. Obviously lots of reservations were canceled. So, it just depends on if you are looking for a place that takes reservations or not. If they don't take reservations, you might be able to just show up. Being able to dry camp sure helps. We have a place not far from where we live we can just show up and usually find a spot even with a larger 5th wheel.
The other issue is size. I like the reservation due to the size of our rig. We found one state part that limits how many reservations they will take, opening the place up for people that just show up. The only issue we had is that we booked what we could get, then tried to change when we got there to an open spot, the camp ground manager wanted us to pay for the reserved spot and pay again for the spot we wanted to move to. Not cool, we just stayed where we reserved. Probably will try that place again this summer by just showing up and seeing what happens. There are some other non official camp spots in the area so we could just park anywhere. It's all dry camping anyway.
