Most information you will need is already been mentioned. Just wanted to add a bit of caution. Be very careful in the heat. I day hike in Florida all the time. Last year, I knew I was going to the Grand Canyon in early October. So I did hiking to prepare. I hiked during the hottest part of the day in Florida in August and September every chance I got, so I would be prepared.
I did a 4 day hike down To the Colorado river …did 2 days of hiking in the canyon and then back up. I didn't have any problems. However, I came across a few people who did.
The first person was someone who was extremely fit and was used to doing a lot of hiking in mountainous regions. Her and her partner and guide were moving at a very good clip downward. They passed me. I caught up with them while they were doing lunch. I passed after a brief chat. Soon they passed me again. About an hour later, I caught up with them again, the female hiker had nearly passed out and was seated while the others were assisting her. They assured me all was okay. They were about 1 mile from the river. Despite the fact that they were in incredible shape and were very accustomed to hiking steep trails they had issues because of the heat.
2 days later I was going back past the intersection of Tonto and Hermits trail. I came across a group of guys who had just descended from the top. They were struggling hard. Again, very good shape and used to hiking in the mountains…..but the heat had did a number on them. (Plus they were carrying big packs and had hiked thru the hottest part of the day.) Luckily, they were 30 minutes from a oasis where they could cool down and get water.
So, please keep in mind that dealing with the heat is a much bigger factor than many realize in the canyon. August is one of the hottest months. ( temps in The canyon can get over 110 degrees) I was there in October…it was much cooler and I still saw people having problems with the heat. I didn't, but only because I am used to hiking in 95 + degree weather and I am a big believer that when it starts to get really hot…one needs to be like the animals and slow the pace down.
When you get to lower parts of the canyon between 11 -4 pm…..it not only is just hot air and the sun you are dealing with….the ground and the rock walls have been baking in the heat all day….and they start releasing that heat. You can be in the shade and still feel the heat coming off those rocks. It is like an oven.
So…please be careful in the heat. Stay hydrated. Do more hiking in the early morning or evening. Be conscious of the effect of moving too fast when the tempature starts hitting those high numbers.
It was sobering to see those other hikers was having issues with the heat while I was in the canyon. It really hit me hard when I read the headlines of the paper 1 hour after exiting the canyon….a day hiker had collapsed and died while I was in the canyon. Granted, he was older. But still….one should not underestimate the power of extremely high tempatures.