When I lived in Wisconsin my chickens would come out in snow and freezing cold IF I shoveled a path from the run to the back of the house ( they loved to hand out under and behind the junipers planted along the house, it was usually snow free and they had protection from the hawks and owls). They almost always came out to the run, even in subzero temperatures but my roofed run was enclosed with clear heavy plastic (leaving a few inches on top uncovered). Even I was pretty comfortable sitting with them as the wind and snow was blocked and the sun warmed it nicely.
Never had heat in the coop. All of mine are heavier birds, never had silkies or polish or bantams though.
Now in southeast Tennessee my walk in run is quite large for 20 chickens, has a metal roof but not enclosed to protect from wind…. It’s in the mid to high twenties now, a bit windy and the flock stays mostly in the unheated coop. They come out for a bit to scratch around, drink and eat but then either go in a corner that has a tarp on 2 sides or go in their very roomy coop. The coop is above freezing even though the pop door stays open, vented under the roofline but I shut the windows as they’re next to the roosts.
It will get colder, at least most nights for a bit but I think we’re good.