Wash. Rev. Code § 35.34.130
The legislative authority of a city or town having adopted the provisions of this chapter shall provide by ordinance for a mid-biennial review and modification of the biennial budget. The ordinance shall provide that such review and modification shall occur no sooner than eight months after the start nor later than conclusion of the first year of the fiscal biennium. The chief administrative officer shall prepare the proposed budget modification and shall provide for publication of notice of hearings consistent with publication of notices for adoption of other city or town ordinances. City or town ordinances providing for a mid-biennium review and modification shall establish procedures for distribution of the proposed modification to members of the city or town legislative authority, procedures for making copies available to the public, and shall provide for public hearings on the proposed budget modification. The budget modification shall be by ordinance approved in the same manner as are other ordinances of the city or town.
A complete copy of the budget modification as adopted shall be transmitted to the state auditor and to the association of Washington cities.
RCW 35.34.130