Note: caffeine and alcohol are dehydrating in the body, so try to avoid them. If you do drink them during this re-hydration program, you would need to drink an extra glass or two of water just to gain back what you will lose. 2. Drink enough water daily. In order to rehydrate a dehydrated body, you need to drink at least one-half ounce per pound of body weight daily. So, for example, if you weigh 180 pounds, you would drink 90 ounces (about 3 quarts) of water. During exercise or hot weather, you should increase your water intake significantly, depending on how much you sweat, how long you exercise, or how hot the temperature is.
How pressure decreases with altitude. As you go higher in the air, the atmospheric pressure decreases. The exact pressure at a particular altitude depends of weather conditions, but a couple of approximations and a formula can give you a general idea of how pressure decreases with altitude.
Therefore, the air pressure is lower. Air temperature changes as you go higher above the earth. Since the surface of the earth heats the air above it, the air is warmer near the ground. Air pressure on the earth's surface also changes. Changes in temperature cause changes in air pressure. As the air near the surface of the earth becomes warmer, the particles becomes warmer, the the particles of the air move farther apart. The air becomes lighter and rises. The lighter air pushes down on the surface of the earth with less pressure.