Pre-chill with ice, not air.

Put a bag of ice in the cooler for an hour or two before you load it. Just leaving it in the shade or filling it with cold air does almost nothing.

The science is simple: ice absorbs a lot of heat as it melts. Air doesn’t. A few pounds of ice inside the cooler will drop the internal temp and chill the walls and lid so your real ice lasts longer. You can use the melted water later for drinks or drain it and replace with fresh ice before packing.

If you’re in a hurry, a few frozen gel packs work too. The key is mass – something with high thermal mass sitting inside. Don’t waste time “air pre-chilling” with the lid open or sticking it in a freezer overnight (the plastic won’t get cold enough to matter).