You need to ware the proper clothing. Light colored, light weight and porous clothing are preferred to heavy clothing. You should not wear sweat suits or rubber type clothing in the heat. This type of clothing increases humidity close to the skin and can cause heat illnesses. On hot humid days if you are wearing a hat you need to remove it every now and then to allow your body to cool down since most of the body heat will escape through your head. If you are having muscle cramps you need to take in more electrolytes. Rainwater collected in clean containers or in plants is usually safe for drinking. This is just something to remember for emergencies, though. Always purify water from lakes, ponds, swamps, springs, or streams. Even deep in the wilderness, most water sources now have Giardia or other unhealthy bacteria and viruses.
Water purification by boiling works fine. Just boil for a minute or two and you are usually okay. The problem is that it is just too much trouble for backpacking. Do you want to stop several times daily to set up your stove and boil enough water to fill your water bottles?First, how much water do you need? This has no simple answer. Your fluid requirements will vary greatly depending on the environment you are in and what you are doing. Backpacking in the Arizona desert, you may be drinking two gallons of water per day. Camping in cooler locations, and not hiking much, you could get by on a fourth of that.
bottom line? Drink as much as you need. If you are very thirsty, or your urine is very yellow, you probably should be drinking more. The important question is this:
How much drinking water do you need to carry to safely and conveniently get you from one water supply to the next?