Chickens are quite the survivors in the winter. The most trouble I have is frost bite on the roosters combs and wattles and it seems the more vasiline I put on them the worse it gets. I have said several times on this site I can't remember in my 40+ years raising chickens of losing one to cold, heat totally different story, lose at least one in the heat of the summer.
Growing up we had chickens runneth over syndrome. (not to mention turkeys, ducks, geese and guienas) I don't think mom or day knew how many we had at any one time, we ordered meat chickens and hen chicks each year from the hatchery but at any time during the spring, summer and fall we had three or four hens running around with chicks they hatched from hiding their nest on the farm. So if I had to guess between 125-150 at any one time. There were six of us kids and we ate a lot of eggs and poultry and did not have a short supply of either.
We had numerous chickens that would roost in the trees at night in the worst of weather, below freezing temp, snow, sleet, you name it and seem to survive just fine.