I'm coming from Northeast Ohio and handled the temperatures fairly well during the 2012 marathon. I think part of this was due to having done some runs on the treadmill at the gym (most of my runs were outside, but sometimes I just got sick of bundling up)...so I did have a few runs in a warmer/slightly humid environment. On race day I made sure I put on sweat-proof sunscreen, ran in the shade as much as possible, and stopped at every water stop along the way. At the water stops I tried to alternate water and Powerade...and obviously I wore cooler clothes (sleeveless shirt, shorts, sunglasses, etc.). If you like running with a hat, I'd suggest investing in a good hat for the race - a breathable one with tech fabric (i.e. the runDisney hat on the
Disney Store website). Yeah, the heat and humidity kill me too...so I know just where you're coming from.