Sections 70A.15.5000 through 70A.15.5220 of the Revised Code of Washington (RCW) and Chapter 173-425 of the Washington Administrative Code (WAC) regulate outdoor burning. Both generally forbid outdoor burning unless specifically authorized. WAC 173-425-050(4) says that:
It is unlawful for any person to cause or allow outdoor burning that causes an emission of smoke or any other air contaminant that is detrimental to the health, safety, or welfare of any person, that causes damage to property or business, or that causes a nuisance
WAC 173-425-060(2)(i) requires a permit for any:
Recreational fires with a total fuel area that is greater than three feet in diameter and/or two feet in height (except in the nonurban areas of counties with an unincorporated population of less than fifty thousand; […]
WAC 173-425-060(5) establishes minimum recreational fire conditions. Those include whether a permit is required or just notification. Even for recreational fires, there are conditions. The regulations limit the materials that can be burned and the days and times burning is permitted. They require fifty-foot s eparation from structures and a maximum burn pile of four feet by four feet by three feet.
Because enforcement differs depending on each agency with overlapping jurisdictions (city police, fire department or fire district, and regional clean air agency) I recommend you consult with your fire marshal, your local clean air agency, and your attorney for specific requirements in your city.