I live on top of a mountain & its already bitter cold here, have had ice and snow. I get up at 5.30am wash & dress & go out to the car to start it & get heater going on the windscreen. I then go back inside for a cuppa and 15 minutes later, leave for work with a nice warm defrosted car waiting for me.
If security is an issue, lock your van/car with the spare and leave it ticking over.