I live in Washington State too, up in Bonney Lake. I don't have heat or light in my coop, but the girls are still laying the same amount of eggs. They are in the coop by 5pm & I don't let them out until 8:30 am when I get home frrom work.
I hate the cold, they don't care. I have a tarp over their run for rain & they have to stay in the run while I sleep, but my mastiff is a Double Agent & will push their pen open & let them run free. In exchange, they let her eat what she wants from their selection of breakfast. Conspiracy!
I move the tractor closer to the house for wind & below freezing & I have an old rug I thrrow over the top, but they seem ok. I am keeping an eye out for anything unusual. A lot of people ask me if I bring them in the house when it gets really cold. I just tell them no, I have knitted sweaters & socks for them!
We are almost neighbors, I live on the outskirts of Orting!mine put themselves in the coop by 4:30 PM, if I don't go out sooner to bring in the water etc., then out at 7:00(daybreak here) sometimes there are several eggs waiting and other days they lay later. The other day I only got 5 eggs, that was a first since last Summer once they had all started laying. Back up to 9 eggs today. can't quite figure out why the decline. Must have been upset for some reason.