For starters, it's important to know that the United States Department of Agriculture does not recommend storing your food outside in the snow as a way to salvage it. This could actually lead to premature thawing and leave the food vulnerable to wild animals even if it still in its packaging. If possible, try to keep your fridge and freezer doors closed for as long as possible because, as the USDA explains, foods can stay cold for up to 48 hours with less exposure to outside temperatures.
Temperature is key when figuring out if your food is still in good shape to eat. Generally, foods like meat, poultry, eggs, condiments like mayonnaise or fish sauce, refrigerated doughs, desserts that contain cream, cheese, milk, and pre-cut fruit and vegetables need to stay at 40 degrees Fahrenheit to stay fresh. Once the temperature of such foods gets any warmer than that for more than two hours, it is likely safer to throw it out than consume it.
There are some foods that can withstand that temperature change, though, including hard cheeses like Parmesan, butter, whole, raw fruits and vegetables, pre-made breads, nut butters, ketchup, and herbs. Of course, shelf-stable foods like canned vegetables, fruits, and meats that do not require certain temperatures for storage are all safe to eat during power outages as well.
When your power comes back on you can also check your freezer items and if you can still see ice crystals on them they are perfectly safe to refreeze. Otherwise, you should safely dispose of the food to avoid food poisoning or other adverse reactions that consuming them may cause. In some areas, exotic wildlife parks will happily accept donations of fruits, vegetables, eggs, and unseasoned meat from your refrigerator for their animals as long as it is not moldy.