State law at RCW 59.20.090(2) clearly states that the landlord must give you 3 months' notice. If you get a rent increase notice that gives you less time, talk to a lawyer right away. Contact info is below.
I'm in the middle of a lease or written contract with my landlord. I just got a notice of rent increase. Do I need to pay the new amount?
No. If your contract or written lease was for a certain amount of rent per month, your landlord cannot try to raise your rent during the middle of the contract. Your landlord must wait until 3 months from the end of your lease.
Example: Your contract ends on December 31. Your landlord needs to have notified you by October 1.