Do any houses use wood for heating, or at least as a backup for times like this? My brother had a wood stove with fireplace that is somehow installed in a way that it heats his ~2000 sqft, 2 story house. I think the system was expensive to install, but it's cheaper for him to use wood than the gas furnace. Granted it doesn't get nearly as cold here in Philly as it does in the midwest or Canada... lowest temp on the 10 day forecast is 14 degrees as a overnight low. Having a backup heat source that is completely independent of the grid is reassuring imo.
Outdoor wood boilers are somewhat popular (don't help much without power though), but I'd hazard a guess that more homes than not just have a small backup generator rather than rely on any kind of wood heat.
Might be different elsewhere; propane is cheaper than the national average where I live, so my experience might be skewed.
If I lived someplace where temperatures went that low I'd certainly want to have backup heat, regardless of what my primary heating system was. Either wood stove or at least a kerosene space heater and a supply of fuel.
When the weather gets that cold, insulation and heating have a hard time keeping up.
Homes that have natural gas furnaces draw so much that utility companies have a hard time keeping the lines at full pressure.
People start using space heaters more and more, which moves the pressure to the electric grid.
The problem with the cold is that it is worse at night, so there's less spare capacity overnight than normal.
At least, this is what we went through in the upper Midwest a few years back. Right now it's -8 and things are running smooth as usual.