The temperature is already climbing. I find that if I drink plenty of water before noon that I can manage to stay hydrated and thus cooler through the afternoon and evening hours.
I have read that if you wait to drink water until you are thirsty then you are already dehydrated.
I don't know it that is true or not, but I do know that I have to be proactive about drinking my water.
First thing in the morning I fill up a quart jar of water and ice and keep it handy. My goal is to finish two quarts before lunch. Seriously, if I drink my water then I seem to be able to handle the heat much better.
In the afternoon I might get tired of plain water so I add a packet of True Lemon. These are little packets of dehydrated fruit. They also come in Orange, Lime and Grapefruit, which is now probably my favorite. You can purchase them at Walmart or Amazon. These little packets have been a big help in kicking my soda habit. My boys like to mix the lime and orange together.