Use water to rinse out the milk jugs completely. Fill each milk jug to approximately 3 inches from the top with water and close the caps.
Freeze the milk jugs in the freezer until they become rock solid.
Pour 3 to 4 inches of cubed ice into the bottom of the ice chest.
Place the ham into the plastic food storage bag to keep the meat safe from any contaminants in the ice chest. Seal the plastic bag securely.
Set the ham on top of the cubed ice in the ice chest.
Add the frozen jugs of water around the ham to surround it with blocks of frozen ice. If you have room for other foods after adding the frozen jugs of water, add other perishable food to the ice chest as well. A full ice chest stays colder longer than an ice chest with unfilled areas.
Close the ice chest lid and pack the ice chest in your vehicle.
Keep the ice chest in a location in your vehicle where the temperature is not excessively high. Avoid the trunk and direct sun.
