COLD STRESS & WORKING IN COLD CONDITIONS 
Just like heat-related stress affects you when working in hot conditions, cold-related illnesses and injuries can be caused by cold stress. The body’s normal temperature is 98.6 °F and is regulated by a variety of physiological factors. When the body temperature is lowered environmental conditions cold-related signs and symptoms appear, such as: shivering, fatigue and pain in the extremities. Skin can also be affected by exposure to a combination of cold conditions and the length of exposure that can lead to frostbite. The links below gives a good overview of cold stress, its effects on the body and what can be done to avoid these conditions.

http://www.osha.gov/Publications/osha3156.pdf

http://www.cdc.gov/elcosh/docs/d0400/d000420/d000420.html