The Right Temperature to Set Your Freezer to Ensure Your Food Stays Safe

We rely on our freezers to store food and safely preserve it, but is your freezer actually cold enough to do the job? Your freezer keeps food cold, which prevents bacteria from growing. This is important because while not all bacteria are harmful, some can cause food to spoil or lead to foodborne illness. Freezers preserve food by halting bacterial activity altogether.

Knowing how cold your freezer should be is crucial to keeping your food safe and well-preserved. We spoke to a food safety expert to learn the correct freezer temperature and how to ensure your freezer stays there.

The Safe Zone 

The correct temperature for your freezer is 0 degrees Fahrenheit—if you set it to 0 degrees (-18 degrees Celsius) and keep it fairly full, it will maintain that temperature.

How to Monitor Freezer Temperature

Gevork Kazanchyan MS, REHS, CP-FS, professor of environmental health at California State University, Northridge, and former public health deputy, says using a thermometer is the best way to accurately monitor the temperature of your refrigerator and freezer. “Take a quick look at the thermometer and then close the door,” he says. The thermometer should be near the front of the refrigerator, he explains, because the deep back is going to be the coldest spot, and placing the thermometer there will not give an accurate reading of the entire freezer. "Don't rely on smart digital thermometers. The old-fashioned ones work great—as long as you don’t drop them," he says.  

How to Make Sure Your Freezer Stays at the Right Temperature

 Kazanchyan shares four tips for keeping your freezer at a safe temperature: 

Keep your freezer full: Your freezer should be full for optimal efficiency, but it also needs good circulation throughout. That means do not obstruct vent openings or overfill it.

Do not add warm food to the freezer: Avoid placing anything significantly warm (above room temperature) directly into the freezer. Instead, rapidly chill it or allow it to come to room temperature before putting it in the freezer.

When adding any food to the freezer:

• Dry off any wet packaging before placing it in the freezer.
• Remove as much air/slack in the packaging as possible.
• Be sure to close lids and seal all packaging to avoid leaving any food exposed.
• If you can, vacuum pack foods intended for long-term freezer storage.

Organize: Store soon-to-be-used items within sight and place foods that will be stored for a longer time in the back of the freezer, where they will not be subject to any temperature fluctuations that may occur at the front when the door is opened.

Keeping Food Safe If the Freezer Becomes Too Warm

What happens if the freezer becomes too warm (say, if the electricity goes out)? And at what temperature should all food be discarded? "In a power outage or natural disaster, leave the door to the fridge and freezer closed as much as possible," says Kazanchyan.

• A full freezer will hold a safe temperature for approximately 48 hours (24 hours if it is half full and the door remains closed).
• Food that still contains ice crystals or is at 40 degrees Fahrenheit or below may be safely refrozen (or cooked), although the quality may suffer. 
• According to the FDA, you should discard any perishable food (such as meat, poultry, seafood, milk, eggs, or leftovers) that has been above 40 degrees Fahrenheit for four hours or more.