I decided to do a 10 k yesterday in the lovely heat, I found that getting yourself over-heated and rather delirious helps, before you know it you forget about the heat and running due to the hallucinations.
I was on top of the world by the time I had finished, with my second skin affect soaked clothes, slicked down hair and bug caked face (sweat is like glue to those critters).
I highly recommend it.