This is a question that I hope none of you ever have to find out about in real life. In my opinion, water is the most overlooked item in our emergency supplies. In general, a healthy person can survive weeks without food. But you won’t survive nearly that long without water.
Making sure you have access to healthy drinking water during an emergency is critical. Do not drink unsanitary water or salt water as that will make you sick and cause you to dehydrate that much faster. As a general rule, if you are in an active environment, you will need to drink two quarts of water per day. You may have heard the rule of 1 gallon of water per person per day. The additional 2 quarts of water are for sanitation and hygiene purposes.
You are especially susceptible to dehydration on very hot or very cold environments. Both of those situations will have dry air that will suck the moisture out of your body. Extreme heat is of course the worst, but dehydration can occur in very cold environments as well. Dehydration will cause your be less efficient and your blood to thicken which in turn forces your heart to work harder. Do all you can to obtain clean, potable water, to reduce activity and to stay in the shade. That is how you stay hydrated.
Now back to the question of how long you can survive without water. This will depend greatly on the temperature. Assuming you are healthy and you have no water and the temperature is 100 degrees or less, you can survive anywhere from 5-10 days. If you are consuming water, even
as little as a quart a day, that number will be extended.