I just saw the weather report and tomorrow night it is supposed to get down to 18 degrees. They're saying its the coldest weather in 25 years. Now I grew up in Buffalo, NY and I'm very accustomed to cold winter weather. However I never had chickens in any winter-like weather before. I only have 2 girls. They have a pretty sturdy coop and a small run they go out in. The coop is behind the house which shelters it from any major weather. Is there anything special I can do to protect them and keep them warm? I'd prefer not to buy a heater, seeing as I will probably rarely use it, if ever, again. Is there anything special I should do or will they be okay for a night?