17 degrees is what I am told sugar soda freezes at, 27 for diets. This is inside of a bay or semi delivery truck. I am sure the van would be similar as far as insulating factor. I wouldn't chance less than 30 if I were parking outdoors myself.
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If what you did yesterday still looks big, you haven't done much today.
I made that mistake with some Sugar Free Red Bull, I forgot to take it out of the back of the van and discovered the next morning 5 cans did freeze and burst open.