Yes, dry ice works – but don't seal the cooler.

Yes, you can. Dry ice keeps things frozen for days. But you absolutely have to vent the cooler and never touch it with bare skin.

Dry ice sublimates (turns straight to gas) and expands to about 800 times its volume. If you put it in a fully sealed cooler, pressure builds up and the lid will blow off – or the whole thing ruptures. So crack the lid or use a cooler with a pressure relief valve. Some Yeti-type coolers have them; others don’t.

Also: dry ice is -109°F. It will freeze-burn your skin instantly. Use insulated gloves or tongs. And never leave it in an enclosed space like a car trunk without ventilation – the CO2 displaces oxygen and you can pass out.

For food safety: don’t let dry ice touch food directly. Wrap it in paper or a towel. Pack it on top, not bottom, because the cold air sinks. Final thought: It’s a great trick for long camping trips – just respect the gas.