Is your refrigerator running? If so, better go catch it.
That was a joke from the 1930s as kids crank-called on the telephone. ("Do you have Prince Albert in a can? Better let him out," was another.)
It's not so funny if your electricity is off - and so is your refrigerator.
When that's the case, you don't have a lot of time before the food in your refrigerator could go bad - only four hours for many foods. The temperature to keep in mind is 40 degrees. Anything perishable - such as raw meat, cooked foods or soft cheeses - that's been warmer than that temperature for more than two hours should be discarded, according to federal food-safety guidelines. Fresh produce generally can be saved, but not prewashed packaged greens. Anything that's been in contact with raw meat juices should be discarded. Do not gauge the safety of food by its smell.
The key is to keep your refrigerator closed - don't dip in there for a glass of milk because each time you open the door you cause the refrigerator to warm up faster. For a list of safety guidelines for specific foods in the fridge and freezer, see www.foodsafety.gov
Freezers, especially full ones, will stay cold for a longer period: full ones, 48 hours; half full, 24 hours.
If frozen foods are thawed or partially thawed, they can be refrozen if there are still ice crystals in the food or if the food was at 40 degrees or below for less than two hours. Depending on the food, its quality may be affected by refreezing, though it will be safe to eat. Check the freezer temperature once the electricity comes back on to assure that it did not go above 40 degrees.
As with the refrigerator, if food has become thawed and has been held at a temperature warmer than 40 degrees for more than 2 hours, it should be discarded.
Dry ice or block ice can help maintain cold temperatures during extended periods. According to foodsafety.gov, 50 pounds of dry ice should keep an 18-cubic-feet freezer that's full of food cold for two days.