IMO a cooler is the way to go for any trunk food. I keep all my truck food in a cooler, even a couple MRE's and coffee. It's summer in SOCAL and things get HOT everywhere, not just in the desert.

Those cheap styrofoam coolers they sell in supermarkets are just fine for a trunk as long as you take care to not crush them.
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Better is the Enemy of Good Enough.
Okay, what’s your point??