Michigan had colder winters than I was used to. Sometimes the temperature would fall below zero Fahrenheit, that is more than 32 degrees below water's freezing point, or lower than -18C. I did not have a car during my first winter there, and it was when I first set out to walk to the shops that I realized I was not going to survive if I continued. I managed to warm up briefly by pausing in different shops as I headed home to thaw out and warm up.
By the second winter I had my old Cadillac. Many residents of the state fit chains on their tyres to cope with icy roads. I never did that, but I did fit winter tyres with extra deep treads. I also routinely used dry gas, an alcohol-based additive you put in the tank to prevent any moisture in the fuel from freezing. Sometimes condensation from the air ran down the sides of the tank, and dry gas stopped it freezing.
I thought jet start was more remarkable. Basically it is an ether spray you squirt directly into the carburettor. When I did this and turned the key, the engine would explode into life. I regularly used both on really cold days, and also carried a stout tow-rope in the boot in case I, or anyone else, needed a pull.
One day I encountered some students by the roadside, next to their car, which had swerved slightly off the road and wouldn't start. I stopped to help, and managed to pull them back to the road. I then squirted dry gas into their engine, and they managed to start it. One said as he thanked me, "Wait till I tell Mom. Last year at Michigan State University, my professor was a small figure on a screen in a room full of hundreds. Here your professors start your car for you!"