Put the cooler in a freezer if you can. Otherwise, fill it with ice the night before.

Yes, pre-chilling works. The goal is to drop the internal temperature of the cooler so your fresh ice doesn’t immediately melt trying to cool the walls and air. If you have a big enough freezer, toss the empty cooler in there for 12 hours. That’s the simplest.

No freezer space? Buy a bag of ice the day before. Dump it in the cooler, close the lid, let it sit 6–8 hours. When you’re ready to pack, dump the melted water (ice will be mostly gone) and load your fresh ice and food. You’ve effectively used that first bag to soak up the heat, not your good ice.

One caveat: if you’re using a rotomolded cooler (Yeti, RTIC, etc.), the thermal mass is huge. You’ll need a longer pre-chill or multiple ice bags. But the principle holds — cold is cold, and you want the cooler itself cold before you put anything inside.

A bag of ice is cheaper than losing half your camping ice on day one.