I read and read and read all about chickens and winters on BYC before getting chicks this fall. Last night 2 of my Black Australorp roosters spend the night out of the coop (oops- although our run is very predator proof) and it was -15F last night. In the coop were the other 16 RIR, RIW and B.As...and the thermometer read -8F as the low. I do have a 100watt heat lamp in the coop on cold nights and a heated waterer. Now, I know that chickens are hearty. Everyone was alright this morning! Although, I will make sure to get all in the coop on cold nights. Its just good to know they can fare just fine in cold weather.
Yep! It's amazing how hardy Chickens (as well as other birds) are during the winter. We're not experiencing temps as cold as yours; however, I've noticed that some of my roosters are preferring to spend the night outside their "sleeping box" (we have temps in the 20's at night).