It's getting HOT!!! High humidity and warm temperatures are reason enough to be sure to get enough water in. Combine that with all of the outdoor exercise that we do, it becomes even more important to stay properly hydrated.
Did you know that if you are 2% dehydrated that you stand to lose up to 20% of your muscle's ability to contract? That means that if you could squat 100 lbs when normally hydrated that you would only be able to squat 80 lbs if you were ONLY 2% dehydrated!!! And guess what? When we 'feel' thirsty we are already about 40-50% dehydrated.
What's the solution? Keep drinking water. Sip all day. Just plain water. If you stay on top of this you can keep your muscles operating at their optimal level.
If you are doing higher intensity exercise or sports outdoors, it may be appropriate to have a good sports drink with you. These drinks can help replace vital salts and fluids and at the same time provide you with some simple sugars to keep you playing hard.