Question: What is the highest and lowest temperature humans can survive in?

Hi pnemono,
This is a good question.

Different people will be able to handle different extremes of temperature. This is often due to conditioning and regulating their heat through behavioural mechanisms.

A further complication with attempting to find limits to human thermal tolerance is that the temperature medium, such as air or water, and exposure time, vastly affects thermal tolerance.

So if you fell into the tropical ocean, with water 20 degrees and no wetsuit, after about 4-5 hours, you would likely be in a hypothermic state. Going in the other direction, sauna temperatures can be 80-100 degrees C and we can tolerate these for a short bit of time.

So we can tolerate broad thermal regimes, but this is because we physiological cope through sweating or shivering, or behaviourally cope through putting on a jumper.

So the best way to think about thermal tolerance is to look at core temperatures. Our normal body temperature is between 36-37 degrees C. So we consider someone to be in hyperthermic state when above 40 degrees C, and hypothermic when less than 34 degrees C. Both of these conditions can be lethal, especially so hyperthermia.