Hi kpgclark!
We were at DL last August (late in the month). It wasn't bad at all! We just took water bottles in backpack and re-filled them at the water fountains. Didn't have really long lines for most things because of fastpasses. We followed the suggestion of someone on these boards and started off in MK early then went to CA Adventure when MK got crowded. I didn't think it was nearly as hot as it gets around Washington, DC in the summer.
Enjoy!
UMTerp