A well built 'root cellar' should maintain a constant temperature year round. That temp will vary some with location, but in general 55° - 60°. That greatly simplified controlling the variables. A hundred years ago people stored milk submerged in mountain streams. Very reliable constant. But burying (root cellar) below ground surface temp level is the most reliable. Also refrigeration is easier - although running the cooling compressor yields heat exhaust so that may need to be vented.
SLIDE WARNING;
Hubby is building a root/storm shelter under a storage shed. So I think a metal can with wet towels would be pretty adequate - we wouldn’t be stocking up like we do now.
Fridge slide
Which bobs comment on root cellars bring to mind a trick my half Indian granny told me. They used to put a silver dime in the milk jug to keep the milk from spoiling.