Below zero temps here in Colorado. Be SURE that the coolant in your car is fresh and can handle sub-zero temperatures.

Driving in sub-zero isn't bad if the roads are dry though I had my steering act locked up because I hadn't moved the wheel in some time (straight interstate) and the power steering fluid was really, really cold.

Since then I've put an adjustable radiator cover on the vehicle for trips in potential sub-zero temps. No steering issues since and the cabin heat works better and the motor oil stays cleaner.