When should I replace the ice in my cooler?

Replace ice when it’s mostly melted because the temperature danger zone for food is 40°F–140°F, and once ice turns to water, the water temperature climbs fast. If the water feels warm to the touch or food starts floating in lukewarm water, change the ice. Block ice lasts longer than cubes—cubes need replacing every 4–6 hours, while block ice can last a full day in a decent cooler.