Wash. Rev. Code § 35.02.139
An election shall be held to elect city or town elected officials at the next municipal general election occurring more than twelve months after the date of the first election of councilmembers or commissioners. Candidates shall run for specific council or commission positions. The staggering of terms of members of the city or town council shall be established at this election, where the simple majority of the persons elected as councilmembers receiving the greatest numbers of votes shall be elected to four-year terms of office and the remainder of the persons elected as councilmembers shall be elected to two-year terms of office. Newly elected councilmembers or newly elected commissioners shall serve until their successors are elected and qualified. The terms of office of newly elected commissioners shall not be staggered, as provided in chapter 35.17 RCW. All councilmembers and commissioners who are elected subsequently shall be elected to four-year terms of office and shall serve until their successors are elected and qualified and assume office in accordance with RCW 29A.60.280.
RCW 35.02.139