The temperature in July when I was at the bottom was approaching 120 degrees. Bright Angel Trail descends 10 miles to Bright Angel Campground and Phantom Ranch, dropping 4476 feet on the way. Also, stop at the cascades just below Indian Gardens to cool off. This trail is called a drainage trail since it follows canyons to the river. The trailhead is right by the lodges in Grand Canyon Village.
Camping is available at the halfway point, Indian Gardens.
South Kaibab Trail descends 4800 feet in only 7 miles to reach the river. No water sources or camping areas exist. It is not recommended to go up by way of this trail in the summer. It follows the ridge line, provides magnificent vistas, but is quite strenuous. The trail head is several miles east of Grand Canyon Village, but shuttle bus service is available.