Upvote:4
Worst idea, I'd say. I made the same mistake - thought I would be able to do it. I went to Grand Canyon in August as well. To say it was scorching hot, would be an understatement. I wasn't just burnt. I melted.
But for all you know, it won't be that hot this summer? Spring is the best time to go there, apparently.
Upvote:5
I was there in August. There were strict instructions for people NOT to try and hike down to the river unless incredibly fit, hydrated and well prepared (Even then, it wasn't recommended).
We walked around the rim trails, and that was pretty hot, and then descended down the Bright Angel trail to the first water hut (1 hour?). That itself was tiring in the hot sun, and then you have to walk back up!
So you can still go, visit, and enjoy it (we were there before sunrise, and just explored non-stop until after sunset) and experience some of being 'inside' the canyon hiking-wise, but be careful, always have water, a hat, and don't overestimate your ability, or underestimate your potential for fatigue.