There are much better and much more experienced cyclists here, but I'll give my .02 living here in Houston. My opinion is you build up to it. You ride the fall, winter, spring and build your miles and speed and then as the temps raise it doesn't hit you as hard. I also found a camelback helped me. For whatever reason I remember to drink more often with a camelback than I do with bottles. I only use the camelback in summer.

YMMV, that worked for me last year when I was training for Hotter N Hell in August. This year I'd be lucky to do 30.