Dear BadKarma...

You can buy one of those tall 'votive' candles.  The ones with pictures of
various religious figures work well.  At night, light the candle.
Surprisingly the warmth of the single candle will make a notable difference
in the internal temperature of the van, even if stuck.  Also provides as a
side benefit, some light, and who knows maybe good fortune or divine
intervention in your predicament.  I prefer plain red.  Having Nuestra Madre
de Guadalupe watching me is not particularly attractive.  Your situation may
be different.

Pensionerd.