Need a method for preserving root vegetables and other food in hot, humid climate in August

Hi to all,

I am looking for a method to keep say a large cooler's worth of vegetables and perhaps some eggs and cheese in a hot humid climate, at least for 90 days without any sort of electricity-based cooling system.  Could I dig a hole in the earth place a flour pot down there and backfill with sand? Wet the sand. Top it off with a clay cap and bricks, maybe some extra humus for insulation but let the wet sand dry out during the day. Would that work thermodynamically to keep my stuff cool? Any other ideas? Float my little clay pot it in a galvanized tub of water for example? Would the effect be the same? Thanks for any assistance.

That is a tall order. How deep are you willing to dig?

In my area, historically, it was common to use hand-dug, cribbed wells as refrigerators. The temperature at 20 ft. below grade was constant.

I have been looking at some temperature/soil and depth maps. (Sigh). Looks like I could get 50 degrees if Id be willing to dig 6 feet.  I may need to.  Wish I knew of some other technology.