landlord tenant laws in WA state, tenant's rights against landlord's service of 20 day notice to vacate

The landlord does not need a reason to end a month to month tenancy. Either party may end the tenancy upon proper notice.

The notice must give the last day of a rental period as the termination date. It must also be served in a manner the strictly complies with the time and manner requirements of the unlawful detainer act.

Assuming the landlord complied with these requirements — which I cannot determine from the facts provided — the landlord may end your tenancy.

The landlord should not enter your property without proper notice. If a landlord enters your property without proper notice you should give written notice of the date and time of the violation. You are then entitled to $100 per violation plus attorney’s fees for future violations. RCW 59.18.150.