Water need not be cold to support you in the heat, but cold water sure cools you off more quickly and feels good.
I'm not a big fan of hot drinks, but to each his own on that.
In the desert heat (and I used to fly a lot in El Centro, CA, in the 110+ heat), and when wearing lots of clothing, you would be astonished at how much water you lose through perspiration. I used to drink a gallon of Gatorade a day in El Centro when I was out there flying, and I was still dehydrated.
I've found that plain water is best, though I will drink Gatorade, or other sports drinks, now and then for a change of pace.
In all honesty, I've spent months in Atlanta, and quite a bit more time in Meridian, MS (similar climate) with and without A/C, and a summer in Pensacola, FL, doing fun activities like running on the beach with an M1 in my hands...while wearing a helmet...
It really comes down to staying hydrated - lots of water. If there is color to your urine, you need to drink more water...
If you're carrying a few extra lbs, then losing them makes a big difference.