-35C is common during Canadian winters, I'm kinda used to it. It can be real nightmare.
But the past years the Jet Stream polar vortex is the worst part, it is either over the UK or Canada, and it's the sudden drop in temps with high winds, and record setting low temps. Just fast, brutal cold comes in. It's hardest on the homeless, elderly and mentally ill.
I fix a lot of furnaces too, clean the igniter/flame rod or just a reboot after condensate drys off. Or a frozen pressure switch.
Propane phase-change from liquid to gas needs heat energy, so the regulator can get below the freezing point. Tank pressure is pretty much zero at -40.
Stress on the grid for electricity is also terrible. I worked in a coal-fired plant and every generating station was maxxed out when it gets that cold. Equipment runs cooler so you don't get troubles but there is no extra capacity if a unit trips.
Most problems are with cars - not enought antifreeze, weak batteries.
Starting a cold car, if an ECU sees the gas pedal is floored at key-on, it will shut off the fuel injectors.
You may need to do this because a cold engine is getting tons of fuel sprayed in, and it will flood in seconds (a few cranks) if it doesn't fire and start. You have around 3-4 seconds to figure it out, or it's call a tow truck and get the car inside a heated garage.
If you think the engine is flooded, put the gas pedal to the floor and crank until it starts running, and then foot off the gas pedal FAST so it doesn't overrev.