Thank you for your question.
In order to file for a dissolution of marriage in Washington, residency requirements must be met for the court to accept the case. If the court discovers it does not have jurisdictional rights to hear the case it will not be accepted or it will eventually be dismissed. The requirements are as follows:
When a party who (1) Is a resident of this state, or (2) Is a member of the armed forces and is stationed in this state, or (3) Is married to a party who is a resident of this state or who is a member of the armed forces and is stationed in this state.
Petitions for a dissolution of marriage, and alleges that the marriage is irretrievably broken will not be acted upon by the court until 90 days has elapsed since the filing and the service of summons on the respondent. (Revised Code of Washington - Title
26 - Chapters: 26.09.010, 26.09.030)
In other words, state law doesn't require you to live in Washington for any specific length of time. As long as you or your spouse has established residency, you can file for divorce within the state. To prove residency, you must maintain a permanent home within the state and have demonstrated intent to make it your primary dwelling. Washington courts also look at things such as voter registration, your driver's license, and mailing address when determining residency.