I have good news for you. Sedum 'Autumn Joy' is a hardy perennial and will handle the winters in your zone, even if there is freezing weather, despite being in a container. You may want to move the pot closer to the house so it does not get swamped by winter rains, and make sure it has good drainage. It is the rain that rots plants in Western Washington, not the cold that kills them. Keep growing, Marianne Binetti