It got down to 7 degrees in the coop last night, and when I opened the door this morning to let them out, they were sitting 5 on the bottom roost and 1 all by herself on the top roost, and they were still all fine . I did feel sorry for the one that was all alone though, usually she has two...
Our remote coop thermometer reads 8° right now, humidity is at 48%. I'm sure the girls are snuggling together (we have 2 roost bars in the coop & they usually sleep 3 &3 when it's really cold), but I know they will be fine.