Congratulations on the new boat!
As Dave says, there are many (Des Moines, Kingston, Edmonds come to mind immediately, plus various ones inside the Locks on fresh water). However, many marinas now have waiting times of up to several years, depending on the location, and that is for uncovered slips. I have no experience with the fresh water options so I'll speak only to the salt water ones.
The larger and more expensive marinas (like Elliott Bay, which is all uncovered) are easier to get slips; smaller and/or and prime locations (Anacortes, Friday Harbor; all uncovered) are 2+ years of wait, and a few (Roche Harbor, Deer Harbor; again all uncovered) are effectively never (10+ years).
However there is a factor in your favor for September: many marinas have winter moorage available from October until May (or thereabouts) which would at least give you an initial place. The difficulty will be finding a covered slip.
My recommendation is to compile a list in your preferred locations and call them all to ask about the options and see, for example, what is involved with their waiting lists. And know that winter moorage somewhere is a backup option if you need it!