Overnight parking requires a permit from the Western Washington Fairgrounds.
The Fairgrounds (253-845-1771) has RV camping available in the "Yellow"
parking lot off 5th St SW for $10 per night.
That includes electricity and water (if it's not too cold -- sometimes
it's shut off to prevent freezing.)
It's not necessary to make advance reservations if one arrives Monday
through Friday during normal business hours.
Stop at the Administration Building (9th & Meridian) to get the permit.
Advance reservations can be made with a credit card for arriving after
Caution: the Western Washington Fairgrounds charges more if they find
you parking without a permit.