Make sure you have a thermometer in your refrigerator and freezer. When the power goes out, check your thermometers for safe temperatures: refrigerator below 40°F, and 0°F or lower for freezer.
Keep the refrigerator and freezer doors closed. When kept closed, a refrigerator will keep food cold for about 4 hours; a full freezer will hold its temperature for about 48 hours; a half-full freezer will hold its temperature for 24 hours.
Freeze water in one-quart plastic storage bags now. These can be used in the refrigerator and freezer to help food stay cold and be a source of fresh water for you to use.
When in doubt, throw it out. Any perishable food that has been above 40°F for two hours or more should be thrown out. Frozen food with ice crystals may be safely refrozen.
Source: Food Poisoning Bulletin