Store it clean, dry, and cracked open.

That’s it. Coolers are simple—there’s not much to winterize. The main risk is mold or mildew from trapped moisture, not the cold itself.

Give it a good wash with soap and water (or a mild bleach solution if it smells funky). Let it dry completely. Then leave the lid unlatched or propped open a crack so air can circulate. Storing it in a garage or shed is fine; the cooler won’t hurt from freezing temps.

One thing to avoid: leaving it sealed shut while damp. That’s how you get a science experiment you’ll have to scrub out come spring.

Don’t overthink this one. Clean, dry, cracked open. You’re done.