Wash. Rev. Code § 2.08.140
Whenever a judge of the superior court of any county in this state, or a majority of such judges in any county in which there is more than one judge of said court, shall request the governor of the state to direct a judge of the superior court of any other county to hold a session of the superior court of any such county as is first herein above mentioned, the governor shall thereupon request and direct a judge of the superior court of some other county, making such selection as the governor shall deem to be most consistent with the state of judicial business in other counties, to hold a session of the superior court in the county the judge shall have requested the governor as aforesaid. Such request and direction by the governor shall be made in writing, and shall specify the county in which he or she directs the superior judge to whom the same is addressed to hold such session of the superior court, and the period during which he or she is to hold such session. Thereupon it shall be the duty of the superior judge so requested, and he or she is hereby empowered to hold a session of the superior court of the county specified by the governor, at the seat of judicial business thereof, during the period specified by the governor, and in such quarters as the county commissioners of said county may provide for the holding of such session.
RCW 2.08.140
Duty to hold court in other county or district: RCW 2.56.040.