In cold climates, heat pumps are usually supplemented with electrical resistance heating (or even gas in some cases). The switch over is automatically controlled by the thermostat. No need for a wood stove or other hassles.
It gets cold every year, you just get used to it. It's not hard.
I'm pretty sure civilization would end over here if Germany had temperatures where F and C come close and heating failed.
The survivors were too stubborn to die so their descendants are often the same.