At what temperature does a person start to freeze? Once again - no straightforward answer to the question😁 Human tissues begin to freeze at -0.5 degrees Celsius. And the freezing process can reach the stage of cell death (necrosis) even at this temperature. But from a medical point of view, it is the internal temperature of the body that matters most. Moderate hypothermia occurs at an internal temperature of 35 ° C. But as soon as it falls below 32 ° C - the body almost ceases to produce heat and the temperature begins to decline rapidly. Consciousness is lost at about 30 ° C, when the temperature drops below 28 ° C severely impaired heart function, and at an internal temperature of 20 ° C - the heart stops.