If it's truly not overheating, I was going to say to replace the temp sending unit too. But if that has been replaced, the next thing to check/replace is the thermostat. You might also have coolant that is freezing or slushing up and doesn't get flowing until the engine warms it a little. Do a sampling of your coolant. If it's not -35 degrees freezing point, add pure antifreeze until you freeze point get down to that temperature. You might have to drain out a gallon to make room for concentrate. The whole system holds about three gallons so make an educated guess how much to add. Extreme engine temperatures is bad for these aluminum head, cast iron block engines so take care of this soon. It's really cold here too Penna.