Frostbite is nasty stuff. Once you have been frostbitten, you can be scarred for life and you can have permanent circulation problems in the affected areas.
You get frostbite when you have skin exposed to severe cold temperatures for a period of time (the amount of time depends on body type, size and other factors). Your body stops sending blood to that area to save the rest of the body. Once this happens, freezing is not long off.
You know when you have frostbite because the affected area is numbed or deadened to feeling. The area becomes white and can have blotchy patches. If you press into the affected area the flesh will not come back into shape immediately. There will be a depression from where you pressed in.
When you come into the warmth and you start to thaw, there will be a tingling sensation and then you can have some pain. It can vary from mild to excruciating. Severe frostbite can result in the affected parts having to be amputated.
The best method for bringing back warmth to the affected area is to use warm (not hot) water. Soak or rinse the area until feeling comes back.
If you get frostbite, seek medical attention.