Or use an electric blanket…
Actually, when I lived in North Dakota I had a lower radiator hose heater. It’s a simple heating coil that goes into the lower radiator hose. It heats the coolant, which circulates via convection. It worked great.
I also used to put corrugated cardboard in front of the radiator. Without that, my engine simply wouldn’t get up to operating temperature, especially on the highway. Some guys used blankets to do the job.