There are various situations where you might want to store a cooler full of food or drinks outside overnight. Is it possible to keep food hot when outside temperatures are low?
What about when it’s warm—how long can food be kept cold?
You can store a cooler outside overnight if you prepare it correctly, which includes either pre-warming or pre-cooling it. The food needs to be layered correctly, and you should minimize empty air. If you are using an inexpensive cooler, it needs additional insulation, which can be easily added.
Read on to find out how to keep food warm overnight.
If you want to keep food cold overnight, we have the steps for that, too. And unless you have an expensive cooler, like a Yeti, you will want to add some insulation, which we also have some tips on.
How To Keep Food Warm Overnight
We call them coolers because we use them to keep our food cool. However, a cooler can also keep food warm.
We use insulation to stop airflow. Think of what insulation does in a house—in the winter, the insulation keeps warm air in the house, but it keeps warm air out in the summer.
Here are two methods to keep food in a cooler warm overnight:
The Brick Method
You will need several bricks, some aluminum foil, and some towels. Put the bricks in the oven for half an hour at 300°F (149°C). Next, wrap them in some foil, and then wrap a towel around them. Place a folded towel on the bottom of the cooler and the bricks on top of that.
The more bricks that you use, the longer your food will remain warm.
Not only that, but you want to have as little air as possible, and some additional bricks help with that. Try to keep bare bricks from touching the cooler material. It is not designed for prolonged direct contact with heat.
Put the food on top of the bricks and then lay extra towels on top. Your goal is to have as little empty air as possible in the cooler.
The Towel Method
Find three to four towels and toss them into a dryer if you have access to one. If not, place them on the hood or roof of your vehicle and let the sun warm them.
Then fold two towels and place them on the bottom of the cooler. Wrap your food in another towel if possible before you put it in. And then place a towel on top. Again, try to have as little dead air as you can.
The towel method makes for a less heavy cooler, but it doesn’t keep food hot as long. It’s an ideal method for when the overnight temperatures don’t get below fifty.
But if overnight temperatures get into the 40s or below, the brick method is recommended.
Prep the Cooler
Prepping the cooler will help in keeping your food hot. To do so, use these techniques:
- Pre-warm. Fill the cooler with hot (not boiling) water and let it sit for 30 minutes to an hour.
- Line it. Aluminum foil will reflect some of the heat into the cooler, so if you have not already done so, then line the inside with foil.
- Fill-in. We’ve already discussed this earlier. Just realize that you must rely on towels. Scrunched up paper will help trap air.
- Add heat. Along with the bricks we mentioned earlier, add heat with hot water bottles or heat pads.
With proper preparation, you should be able to keep food warm overnight.
But what about if you want to keep food cold? Read on for tips on how to do that.
How To Keep Food Cold Overnight
Some of the techniques for keeping food cold are similar to those for keeping food warm. The cooler’s insulation helps reduce the transfer of heat energy.
You have read how to keep heat in. Here are tips for keeping heat out.
Prechill and Prechill
If your cooler is warm, the heat energy inside melts some of the ice until the air temperature reaches thermal equilibrium. A pre-chilled cooler will have less heat energy to dissipate.
Keep in mind that the ice used to chill the cooler will need to be tossed, so many people use frozen water bottles or reusable ice packs.
Putting warm food in a chilled cooler will have a similar effect to putting cold food in a warm cooler—the food will warm up the ice. So whenever possible, pre-chill your food before putting it in the cooler. That way, the food is working with the ice, not against it.
Layer for the Cold
Warm air is less dense than cold, which is why warm air rises and cold air sinks. So if you put cold foods over warm foods, warm air will cool them more quickly than if you put the coldest foods in first.
So layer your cooler with the coldest food on the bottom, your primary ice source on top, and foods that you want ready access to on top of that.
You’ve probably heard it a thousand times, but keep your cooler closed as much as possible.
Whenever you open the cooler, you let warm air in. Open the cooler as needed, but don’t check on it to see if the ice has melted. Trust the cooler.
Ice, Ice, and More Ice
The more ice you put in your cooler, the longer food and drinks will stay cold.
On the other hand, too much ice and there won’t be room for food. A rule of thumb is a 1:1 ratio of food to ice. Some recommend a 2:1 ratio, but if you pack your cooler well, you will not need that much ice.
- Because large ice has less surface area, it melts at a slower rate. Making large blocks of ice is as easy as filling an empty container with water and freezing it.
- Spheres of ice melt at a slower rate than cubes, so consider freezing water-filled balloons.
- Ice packs have several benefits. They are reusable, melt at a lower temperature than ice, and keep your food dry.
- Try to eliminate pockets of warm air using ice cubes, towels, or foam.
Add Insulation to the Cooler
Very few coolers would not benefit from some added insulation—even expensive ones like Kong or Yeti.
Even on a pricey cooler, an insulating mat placed on top of your food and drinks will help keep cool air in.
If you custom-fit it to your cooler, you only lift enough of the mat to get what you want when you open the cooler. Here are additional suggestions for improving your cooler’s insulation.
- Beef up the walls. The difference in wall thickness between a cheap and expensive cooler can be as much as 2 inches. Add insulation walls using Styrofoam, polyurethane foam, or double reflective insulation.
- Insulate your lid. Many cheaper coolers have no insulation inside their covers. An insulated lid does a better job of keeping cold air in. Some people insulate the lids by inserting spray foam, but this is a messy job, so another option is to attach a rigid foam board to the cooler’s lid.
- Add a gasket. Use foam or weatherstripping to create an airtight gasket around the lid.
Storing a cooler overnight can be done whether you want to keep food warm or cold. Pre-cool or pre-warm, place the hottest or coldest food on the bottom, and make sure to seal the cooler.
Adding extra insulation is also an excellent idea if you have an inexpensive cooler.
- Outside Online: How to Properly Pack a Cooler
- Michigan State University: Can You Safely Store Perishable Food Outside
- The Boat Galley: How to Use an Ice Box Cooler for Food Storage
- Love to Know: Camping—Tips on Keeping Food Frozen in a Cooler
- Express UK: Can You Keep Your Turkey Outside?
- Hunting Waterfalls: 10 Ways to Insulate a Cooler
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