I was in a used Honda Civic. It had some body damage, both caused by my error and one that came with the vehicle.
I parked near a old, beater MG in Alabama. It dropped to 7 degrees that. I had a heater, but slept in a Artic rated sleeping blanket and two layers of clothing.
Cops couldn't tell the difference whether I was in the car or not, the windows froze over.
I was hassled by a Oneonta Police Department LEO while I was taking a short break before work in a cemetery where no one ever visits. It was ridiculous. I was in a Ford Dealership parking lot in the Used Car sections.
It worked out very well, went to the gym to shower and made off and explored.