My babies are 5 weeks old and appear fully feathered. It's warm ish here in Tennessee and they are fighting coming in the house by avoiding me and my daughter when we go for them. They are huddling from time to time but aren't looking cold per say. Again if we attempt to grab em they run. Mind you they fight going outside too but only cause they don't want to be handled. My daughter opened the door to let them decide and it works for her until today. It's 52 and according to the weather forecast shouldn't get any cooler tonight. 65 tomorrow. They have a very small house without a door that has 4 nesting boxes. Pictures of the coop, my babies, chicks and forecast included for reference. The house now has a run I made so they are predator safe.
I think they will do just fine. They have each other for warmth and this gets then cold hardy head on. I've had chicks outside one day old in 20 degree weather foraging with their mama all day and they did just fine and are some of my best layers now.im in Alabama so the weather is similar. I put my 2 youngest out last week in the coop at night with the adults and it was colder than it is now and they did great. I think they are ready!