1. passengers seat, lay your cloths out as if you were wearing them in that seat and blast the heat (seat heaters help
2. if you heat is on you are getting fresh air from outside the car
3. running your car at night will use max 1 gallon of gas, $4 is much cheaper than a hotel room or rent, you can run your car all night with the heat on and window cracked, stay warm and dry your stuff, I usually run my car for a few hours before sleep, getting everything hot as hell and dry, then turn it off when i am falling asleep, wake up cold 5 or 6 hours later and run the car for an hour or so while i go back to sleep, wake up hot, turn the car off, go back to sleep, wake up with beautiful mountain in front of you at sunrise, warm the car back up, get dressed, go skiing