Ground cooler

Dig a three foot deep hole by three foot squared, (or larger, smaller depending on your needs).Build a insulated top for the hole, add a rack to keep item off the bottom.(or not)

Or, if you have water tight containers, you can just dig a hole, add container and fill the hole back in with the dirt until needed. But it does need to be at least a foot deep to reach the cooler earth.

The ground will adsorb heat and the hole will remain cool, at least cooler than the outside temp.

I will say this, it needs to be in a place where rain water will not get in and fill it up.

This works like a old time root celler, dark and cool.