Frostbite occurs in three stages, with each stage more severe than the last.
Stages of Frostbite
The first stage of frostbite is a mild form called frostnip. During this stage the skin turns pale/red and feels extremely cold. If the exposure continues the person will develop a tingling and numbness. As the skin warms it may be painful, but frostnip does not do permanent damage to the skin.
2) Superficial Frostbite
The second stage is superficial frostbite. During this state the reddened skin turns white or pale and may remain soft to the touch. However, during this stage the tissue may start freeze. When rewarming it’s possible for the skin to turn a blueish purple and the person may experience burning and swelling. It is possible that blisters will form up to 36 hours after rewarming.
3) Severe or Deep Frostbite
Severe or deep frostbite is the final stage. During this stage all tissue layers freeze. The affected person may lose function of areas, experience pain, and lose sensation of the cold. Blister may form up to 48 hours after rewarming and the tissue will harden and turn black as it dies.
Source: Mayo Clinic