The short answer some legislative input is required but it is limited. There seems to be no limit to the length in the State of Washington.
The Governor has extended the isolation segment of his emergency declaration until May 4th 2020; continuing to shut down the economy and many business’ futures.
This brought to mind a concern of many: how long can the Governor shut down the state without any other accountability.
The RCW found here contains the information on this article: http://apps.leg.wa.gov/RCW/default.aspx?cite=43.06.220
The following excerpt explains how the legislature can be involved. The pertinent part where the legislature is mentioned is toward the bottom of the page of the RCW link above.
(4) No order or orders concerning waiver or suspension of statutory obligations or limitations under subsection (2) of this section may continue for longer than thirty days unless extended by the legislature through concurrent resolution. If the legislature is not in session, the waiver or suspension of statutory obligations or limitations may be extended in writing by the leadership of the senate and the house of representatives until the legislature can extend the waiver or suspension by concurrent resolution. For purposes of this section, “leadership of the senate and the house of representatives” means the majority and minority leaders of the senate and the speaker and the minority leader of the house of representatives.