The official numbers: a closed refrigerator keeps food safe for up to 4 hours without power. A full freezer holds a safe temperature for approximately 48 hours (24 hours if half full), as long as the door stays closed. These figures come directly from USDA Food Safety and Inspection Service (FSIS) guidance, and they’re the numbers this site has referenced throughout its outage-preparedness content [→ /outage-prep/power-outage-checklist/] — this page is where they get the full, detailed treatment: the exact thresholds, what to do at each stage, the refreezing rules, and the definitive keep-or-toss guidance by food category.
The Two Core Rules
Refrigerator: 4 hours, door closed. After 4 hours without power, the USDA advises discarding refrigerated perishable food — meat, poultry, fish, eggs, and leftovers specifically named in official guidance. This assumes the door has remained closed; every opening shortens the effective window.
Freezer: 48 hours full, 24 hours half-full, door closed. A full freezer has enough thermal mass (frozen food packed together) to hold a safe temperature far longer than a refrigerator. A half-full freezer has less mass and less insulating effect from neighboring frozen items, cutting the safe window in half.
The temperature thresholds behind both rules: food safety guidance centers on 40°F (4°C) for refrigerated food and 0°F (-18°C) for frozen food. The 4-hour and 48/24-hour figures are estimates of how long a closed appliance takes to drift out of the safe range under typical conditions — an appliance thermometer (kept in both the fridge and freezer at all times, not just during outages) is the only way to know your actual numbers rather than relying on the clock alone.
The Discard Rule, Precisely
Official guidance is specific and worth quoting precisely because “when in doubt” decisions during a stressful outage benefit from a clear rule rather than a vague feeling:
- Discard refrigerated perishables — meat, poultry, fish, eggs, soft cheeses, milk, and leftovers — after they’ve been above 40°F for 2 hours or more. In practice, this generally aligns with the 4-hour closed-door window, since a closed fridge typically takes about that long to rise above 40°F in the first place.
- Never taste food to determine whether it’s safe. This appears in every version of official guidance for a reason: you cannot taste, smell, or see dangerous bacterial growth — foodborne pathogens don’t reliably announce themselves through spoiled taste or smell.
- When in doubt, throw it out. This isn’t a throwaway phrase (no pun intended) — it’s the official closing line of USDA’s own guidance, precisely because the cost of a wrong guess (foodborne illness) vastly outweighs the cost of discarded food.
Refreezing: What’s Actually Safe
A common point of confusion once power returns — official guidance is clear:
Food is safe to refreeze if it still contains ice crystals, or if it registers at 40°F or below on a food thermometer. Refrozen food may lose some quality (texture, flavor) compared to food that was never thawed, but it remains safe to eat under these conditions.
Food should be discarded if it has been above 40°F for 2 hours or more — the same threshold that governs refrigerated food, applied to thawed freezer contents.
One notable exception: ice cream. Once melted and refrozen, ice cream’s texture changes significantly and food-safety guidance specifically flags it as a discard item regardless of temperature readings, separate from the general refreezing rule.
What to Keep vs. Toss, by Category
Discard after 4 hours without power (or 2 hours above 40°F), no exceptions:
- Raw or cooked meat, poultry, and seafood
- Milk, cream, and soft cheeses
- Eggs and egg-based dishes
- Leftovers and deli items
- Soups, stews, and casseroles
- Cut fruits and vegetables
- Anything with mayonnaise or cream-based sauces
Generally safe longer than 4 hours (use judgment, check for spoilage signs):
- Hard cheeses (cheddar, parmesan, and similar)
- Butter and margarine
- Whole fruits and uncut vegetables
- Bread, jam, and condiments with high salt, sugar, or acid content (ketchup, mustard, most salad dressings)
- Opened, hard alcohol-based items
Freezer contents, once power returns:
- Safe to keep/refreeze: still has ice crystals, or reads 40°F or below on a thermometer
- Discard: no ice crystals present AND above 40°F, or has been above 40°F for 2+ hours (with the ice cream exception noted above)
If uncooked meat juices dripped onto other food during thawing: discard the contaminated food as well, even if it would otherwise fall in the “safe” category — cross-contamination follows its own rule regardless of the affected food’s individual temperature history.
Extending the Windows: What Actually Works
1. Keep doors closed — the free, zero-effort action that matters most. Every unnecessary opening lets warm air in and shortens both the 4-hour and 48/24-hour windows. This is worth saying explicitly to every household member the moment an outage starts [→ /outage-prep/power-outage-checklist/].
2. Keep the freezer full deliberately, even with non-food items. A full freezer holds temperature roughly twice as long as a half-full one — filling empty space with frozen water jugs, bags of ice, or gel packs before an anticipated outage (a forecasted storm, for instance) genuinely extends your safe window [→ /outage-prep/hurricane-power-outage-prep/].
3. Use a cooler with ice once you’re past 4 hours. If the outage extends beyond the refrigerator’s safe window, transferring perishables to a cooler packed with ice or frozen gel packs — maintaining 40°F or below — is official guidance’s recommended next step, not an improvisation.
4. Dry ice for extended outages. Roughly 50 pounds of dry ice can hold an 18-cubic-foot full freezer for about 2 days. Never touch dry ice with bare hands, and never let it directly contact food — both are real hazards, not just cautionary notes.
5. Generator or battery power targeting the fridge specifically. Even a small portable generator or power station running the refrigerator for a few hours a day resets both clocks entirely — this is precisely the duty-cycle strategy this site recommends throughout its portable generator content [→ /portable-generators/what-size-generator-runs-refrigerator/], and running the fridge is consistently the single highest-value use of limited backup power.
The Appliance Thermometer: The One Prep Step Worth Doing Today
Every official source converges on the same recommendation, and it’s worth acting on before your next outage rather than during it: keep a thermometer in both your refrigerator (40°F or below) and freezer (0°F or below) at all times. When power returns, reading these thermometers — rather than guessing based on how long the outage lasted — gives you a definitive, individual answer for your specific situation, since actual conditions (how often doors opened, ambient room temperature, how full each appliance was) vary enough that the standard hour-based guidance is an estimate, not a guarantee.
Cost: $5–$15 for a basic appliance thermometer. Time: two minutes to place them. Value: replacing “I think it’s probably fine” with an actual number, every single outage for the life of the thermometer.
Frequently Asked Questions
How long does food stay good in the fridge without power? Up to 4 hours with the door kept closed, per USDA guidance. After that, refrigerated perishables (meat, poultry, fish, eggs, dairy, leftovers) should be discarded.
How long does a freezer stay cold without power? A full freezer holds a safe temperature for approximately 48 hours; a half-full freezer for about 24 hours — both assuming the door remains closed throughout.
Can I refreeze food after a power outage? Yes, if it still contains ice crystals or reads 40°F or below on a food thermometer. Discard food that has been above 40°F for 2 hours or more, with ice cream as a specific exception that should be discarded once melted regardless of temperature.
What temperature is food unsafe at? The safety threshold is 40°F (4°C) for refrigerated food. Perishable food held above 40°F for 2 hours or more should be discarded, per USDA/FDA guidance.
Should I throw out food if I’m not sure how long the power was out? When genuinely uncertain, yes — official guidance’s own phrase is “when in doubt, throw it out,” precisely because you cannot determine food safety by taste, smell, or appearance alone.
Does opening the fridge briefly during an outage ruin all the food? Not automatically, but every opening lets warm air in and shortens the safe window — brief, necessary openings are far less damaging than leaving the door open or opening it repeatedly “just to check,” which is the behavior most likely to push food past the safe threshold early.