We live in Missoula Montana. It has been getting pretty cold up here, very cold. It gets below 0 on all the nights. WHen I was putting them away two of my six chickens would not get out from under the bunny hutch. I tried to get them it took a long time! It was wierd because those were two who were always super sweet. When I finally put them in I checked that they had water and food, they did. Then I made sure the heat lamp was on, and closed the door. When I went to let them out, one was on the floor of the coop, lieing on her face. I went inside and yelled for my dad to help me. We took her out, but she was already dead. She didn't smell or anything, and was a good wieght. She might of died of exposure, we do have a foot of snow. They usually don't go in the snow. I think I am going to take out all the litter and replace it. I have the deep litter method going on, I know I shouldn't take it all out for that, but I if it is a desease I want the bacteria to die. I also have the coop open, hoping the cold kills any bacteria, the chickens do have a cozy snug place to hangout in. If one looks off, I think I can take her inside for the night and help her a little. I really hope none die, these are my first chickens the one that died was my favorite too. I was happy that none had died yet, I thought I was doing well for a newbie, but I guess not.