A bodies internal temp can only survive up to 108F it starts to die around 105F which is when the proteins inside the body begin to cook apart. As far as the coldest the human body can get is in the 70'sF and potentially lower depending on the time spent at the temp.'m not sure but I believe once an external temperature above 212 degrees is reached a human will begin to die because of their internal fluids simply starting to boil, remember we are 70-90% water.. The coldest temperature your body can get before shutting down and going into hypothermic shock is 89 degrees.