A closed refrigerator keeps food safe for about 4 hours after the power goes out. A full freezer holds its temperature for roughly 48 hours, or 24 hours if it’s only half full. These timelines assume you keep the doors shut as much as possible.
The 4-Hour Rule for Your Fridge
Your refrigerator needs to stay at or below 40°F to keep perishable food safe. Once the power cuts out, the insulated walls buy you time, but not much. After about 4 hours, the interior temperature starts climbing into what the USDA calls the “danger zone,” the range between 40°F and 140°F where bacteria multiply rapidly, doubling in number in as little as 20 minutes.
Every time you open the door, you let cold air escape and warm air in, which shortens that window. If you know the power will be out for a while, resist the urge to check on things. Decide what you need before opening, grab it quickly, and close the door.
Your Freezer Lasts Much Longer
Frozen food is far more resilient. A packed freezer acts like a giant ice block, with each frozen item helping keep its neighbors cold. That’s why a full freezer maintains a safe temperature for about 48 hours without power. A half-full freezer loses cold air faster because there’s more empty space for warm air to fill, cutting that window down to roughly 24 hours.
If you know a storm or planned outage is coming, you can improve your freezer’s staying power by filling empty space. Freeze containers of water ahead of time and pack them into gaps. This adds thermal mass that slows the temperature rise, and the melting ice can later help keep your fridge items cool too.
Which Foods to Keep and Which to Toss
Not everything in your fridge needs to be thrown out after a power outage. The 4-hour rule applies specifically to perishable items: raw or cooked meat, poultry, fish, eggs, milk, soft cheeses, cut fruits and vegetables, and any cooked leftovers. These foods support bacterial growth quickly once they warm up.
Shelf-stable items are fine to keep. Condiments like mustard, ketchup, and soy sauce, along with hard cheeses, butter, whole fresh fruits, and unopened jars of peanut butter or jelly, can handle the temperature swing without becoming unsafe. Use common sense here: if something looks or smells off, toss it, but a sealed bottle of hot sauce is not going to go bad in a few hours.
The tricky part is knowing what happened to your food if you weren’t home when the power went out and came back on. If you don’t have a thermometer in the fridge, you’re guessing. An appliance thermometer (the kind you leave inside the fridge permanently) takes the guesswork out of it. If the thermometer reads 40°F or below when power returns, your food stayed safe regardless of how long the outage lasted.
When Power Comes Back On
For your freezer, the key indicator is ice crystals. If food is still partly frozen, still has visible ice crystals, or feels refrigerator-cold (40°F or below), it’s safe to refreeze or cook. You don’t need to cook raw items before putting them back in the freezer. The texture of some foods may suffer after thawing and refreezing, but they’ll be safe to eat.
Discard any food that has been above 40°F for more than 2 hours. This is the firm cutoff from federal food safety guidelines. Also throw away anything that has been in contact with raw meat juices, even if the temperature stayed cold enough, because cross-contamination creates its own risk.
How to Extend Safe Time
If you’re expecting a long outage, a few simple steps make a meaningful difference:
- Group freezer items tightly. Push everything together so frozen items share cold with each other rather than cooling empty air.
- Use ice. Bags of ice from a store can go directly into the fridge to hold temperatures down well past the 4-hour mark. Block ice lasts longer than cubed ice because it melts more slowly.
- Move perishables to a cooler. If you have a good cooler and enough ice, transferring meat, dairy, and leftovers buys you extra hours without needing to open the fridge at all.
- Keep doors closed. This is the single most effective thing you can do. Every opening costs you cold air you can’t replace.
Dry ice is another option for extended outages. Placed in the freezer (never in an enclosed room without ventilation), it keeps food frozen far longer than regular ice. If you go this route, handle it with heavy gloves and never touch it with bare skin.
The Cost of Guessing Wrong
Food that looks and smells perfectly fine can still harbor dangerous levels of bacteria. You cannot tell by appearance whether something has been in the danger zone too long. Foodborne illness from improperly stored meat, dairy, or eggs can cause symptoms ranging from a rough couple of days to hospitalization, especially for young children, older adults, and anyone with a weakened immune system. When in doubt, throw it out. Replacing groceries is always cheaper than dealing with food poisoning.