There is no beating the heat, particularly when it comes to running. Summers are great for the long days and slower pace, but the high temperatures and humidity make them not so ideal for running. A couple weeks of warm-weather running, though, gets the body acclimated. But acclimation is the hard part.
I have a particular aversion to heat. Twice I've ended up in the hospital with pretty severe dehydration during long runs, including the horrific Delaware experience where I was dragged across the finish line. I really don't deal well with heat.
I ran five miles at about 7:15 pace. Ideally, I'd do a long run this weekend, but it's not important enough to go through that kind of suffering. It wasn't pretty, and I'm still sweating an hour and a half and a shower later. The only way to deal with the heat is adjust the pace, drink tons and eat some salty food to retain water better.
5 miles, 36:13