I got my "outdoor coop ready" starter pulletts a few days ago. They are about 7 weeks old and doing well so far. A storm is moving in and the next 3 nights it's supposed to be colder around 25 degrees Farenheight with up to 10 inches of snow. Should they be ok? There's no heat in the coop and no adult birds. I've kept the coop closed up all day to keep any warmth they generate in there, but will this be good enough? Considering putting a hot water bottle in there when I go to bed. Other suggestions? Am I worried needlessly? They are my first chickens and smaller than I'd expected when I picked them up.