I think that I may have frostbite. How would I know for sure?

Look for... ...White, red, and yellow patches of skin that is numb. In more severe cases blisters develop 1–2 days later, then become hard and blackened (but usually appear worse than they are). If the area freezes further, deep frostbite occurs, causing damage to muscles, tendons, blood vessels, and nerves. That is a serious situation, sometimes resulting in loss of fingers or toes.