Although I keep blankets, Heatsheets and a sleeping bag in my car, I think I might rely on my car's heated seats. My current car has 3 levels of heat for the front seats. The highest one is pretty toasty. I don't know what current draw is but I suspect on the lowest setting I could get more than a few hours of continuous warmth, probably much more with intermitten use and the occasional running of the car engine to boost the battery. I will have to check to see if they work with the engine off, but the battery on. Combined with blankets and warm clothes I think I'd be set.

My best plan is to stay home. I'm now old enough and secure enough to refuse to drive in bad weather. My days of driving through blizzards for work are over.