No, but the June average high is 93 and all the trails are pretty much middle-of-nowhere beating-down-sun. It isn't just hot, your body doesn't cool the same way because the sweat evaporates too fast. If you break down or have to stop, you're only shade is under the vehicle.
We've been in early October the past two years and it is still in the 80s (50s at night). Even that late in the year you still have to be VERY careful about dehydration. We're not talking a couple of bottles of Dasani, we're talking about over a gallon per person. You're really better off avoiding caffeine and alcohol completely, but definitely for the first day or two. I got sick the first day the first year we went and I *thought* I was drinking plenty.
I'm sure you'll have fun, but it will definitely be more fun if you don't feel like sh*t. 
