First Degree: Skin turns red and feels very cold.
Second Degree: Skin turns white or very pale, and blisters may appear upon warming.
Third Degree: Area turns black and hard as tissue dies.
• Avoid rubbing the area, especially with snow.
• Don't walk on frostbitten feet or use a frostbitten hand.
• Avoid thawing the affected area if you are far from help or if there is a chance of refreezing.
• To thaw, immerse area for 20-45 minutes in tepid water; never use hot water.
• Do not put salves or creams on frostbite.Source: Hennepin County Medical Center