Keep the freezer closed to keep the cold air in. A full freezer will stay at freezing temperatures for about 2 days; a half-full freezer about a day. If the power will be out for several days use dry ice to keep temperatures cold. Twenty-five pounds of dry ice should keep a 10 cubic-foot full freezer 3 to 4 days. If foods still contain ice crystal they should be safe and can be refrozen if they have started to thaw. Refrigerated items should be safe as long as power is out no more than a few hours. The best way to determine if foods are safe are use a thermometer in your refrigerator and freezer. If the temperature remained below 40 degrees during the power outage the food should be safe to eat.