I am just not seeing it, most of the weather sites that I use are showing normal summer temperatures over the fourth of july weekend.
Of course it is still a ways out there and this phenomenon could very well have an effect, we will probably know more in the coming week.
For tips on hydration:
Remember that becoming and staying hydrated is something you should prepare for the night before. Drink plenty of water (the night before as well as the morning of), and avoid alcohol use or other drugs. Do not drink carbonated soda, and if you expect to sweat a lot, bring some Gatorade or other water with added electrolytes to avoid getting muscle cramps due to loss of electrolytes. If you start to feel faint, exhausted, or dehydrated, get indoors in an air-conditioned room ASAP and take a break. Look out for each other and keep an eye on the others in your group in case anyone needs help.