I don't know how cold it gets where you are. I'm in zone 7 and don't do anything extra. When I had to leave overnight for an emergency, I put an aquarium heater in the
water so it wouldn't freeze. They have the chicken house and two dog houses for shelter. I wish I still had the picture of a snowy evergreen tree infested with chcikens😀 Most of mine tend to like walking through the snow leaving dinosaur tracks. Only have a few birds that don't want to leave the house. The rest still leave the run when I let them out to free range.
Sometimes on bitter cold days, I'll make a warm mash which they seem to like.
We did have a possum that tried to go after the ones in the tree and the dog was having a fit since he couldn't get to it. Dog and rooster made
enough noise to wake us at 1 am so we could help it on its way. No chicken loss fortunately.
Over all, cold weather and snow doesn't seem to phase them at all. They have a harder time on high heat and humidity days.