Wash. Rev. Code § 35.20.200
The presiding municipal court judge shall, from attorneys residing in the city and qualified to hold the position of judge of the municipal court as provided in RCW 35.20.170, appoint judges pro tempore who shall act in the absence of the regular judges of the court or in addition to the regular judges when the administration of justice and the accomplishment of the work of the court make it necessary. The presiding municipal court judge may appoint, as judges pro tempore, any full-time district court judges serving in the county in which the city is situated. The term of office must be specified in writing. While acting as judge of the court, judges pro tempore shall have all of the powers of the regular judges. Before entering upon his or her duties, each judge pro tempore shall take, subscribe and file an oath as is taken by a municipal judge. Judges pro tempore shall not practice before the municipal court during their term of office as judge pro tempore. Such municipal judges pro tempore shall receive such compensation as shall be fixed by ordinance by the legislative body of the city and such compensation shall be paid by the city except that district court judges shall not be compensated by the city other than pursuant to an interlocal agreement.
RCW 35.20.200
Judges pro tempore appointments: RCW 3.02.060.