I live in interior Alaska and I beg to differ about chickens not getting too cold in winter. I have an insulated coop - a cabin for them and I have a 100 watt infrared lizard light on all the time about 18 inches off the pine shavings. I also have an Eco Heater on the wall (7' x9' coop) which is on a thermostat which turns on the heater at 35 above zero and off at 45 degrees. There are two partially blocked attic vents (blue foam boards) on opposite so there is a constant flow of cold air coming in. That floor area gets quite cold and the eggs are quite cold in the nests if I haven't gathered in a couple of hours.
Now, how do I tell that chickens are cold? I open the pop door and they rush out. They come in and out and in and out until they all decide to come in. I shut the pop door, sit down on the floor and some come to hunker down on my legs/thighs. To my surprise, the barred Rocks (from New England originally) shiver. I cannot see the shiver, but I can feel them shiver, quit, shiver again, quit, etc. until all shivering goes away. To look at them and to observe their behavior if I don't sit down, I would not ever suspect that a few of them were actually cold enough to shiver. So, I often unplug the eco wall heater from the thermostat, leave it on all day, take out a piece of the blue foam and let the air exchange get larger.
In the morning, when the heater has been on the thermostat, I will also sit down for an extended period of time. About four to six of the dozen, 7 month old hens, will rush to my legs to warm up before deciding they are good to go.
As for as minimum outdoor temperatures where I live, we have cold snaps like everyone except the numbers are larger than in the lower 48. Usually. It seems like there will be a dreadful cold snap of 25 to 50 below zero and then things moderate to a steady 8 or 10 below for extended periods.
