Drink a lot of water, like carry it around with you in your bag. Seriously. Native here, and it's been killer hot. Today we finally got some decent rain but that's short term in late August/early September. The city is extremely hot, especially if you don't use the hamster tunnels because nothing in this city is flat. So get a water bottle when you get here and keep refilling it. Water is provided in the Hyatt in little plastic cups, but that's not a long-term plan.

Oh, and the bag: I have a small mini-messenger bag I carry to the con with me so I don't have to hold anything really. I actually got it a store in Peachtree Center in 2006 but it's been darned useful since. It's also harder for a purse snatcher to snatch something that's literally attached. And mine is big enough to hold the pocket program, the big book/autographs, all the necessaries (wallet, lipstick, insulin), some granola bars and my water bottle. It's definitely a wise investment to find something that distributes the weight.