How long can humans last without water?
I don’t buy the 3 hours without shelter bit. My outdoor survival training has taught me a rule of thumb like this. But you are all misunderstanding what the world “shelter” really means in that context. It is talking about protection from the elements. So shelter includes clothes, tents, houses, cars, hats, sunscreen, etc. When I go hiking in the Rockies, I always have the shelter to survive out there for days, if need be. I don’t ever take a tent hiking. In the summer in most parts of America, the clothes on your back are enough shelter to survive in the wild until mid-Fall. And they just chose 3 as a mnemonic device. Shelter comes first, as you need it badly unless you are on a temperate, tropical island. In the arctic you will have minutes without shelter (meaning, you were out there naked). Most places you’ll last much longer, especially when you assume most people have at least some “shelter” with them when they end up in a survival situation.
As a nutritionist, the figure for survival I’ve repeatedly heard is 48 hours without water and two weeks without food. Of course this varies on so many different factors, as others have pointed out. It should be noted though that it’s not as if from the point when you stop consuming liquid, to the point that you die, you’ll be able to function at full capacity. Death by dehydration is a nasty process involving incessent skin irritation, halucinations, and the swelling/ cracking of the tongue.
