When you go hiking, staying cool is probably high on your priority list, especially if you will be doing this in the hotter months of the year. You can stay cool by staying hydrated.
Carry a hydration pack. These are great in that they allow you to take sips without reaching for your bottle, which will increase the frequency at which you do it.
You can also carry a squirt bottle. Spraying some water on yourself can be amazingly refreshing. You can also combat the heat by placing a cloth soaked in cold water around your neck or head.