The National Park Service seems to believe that park visitors can never hear too much about smart hiking, the dangers of heat, and the importance of water. The message turns up on park publications, at trailheads, and on bulletin boards in and around the park. Despite the ubiquitous message, many hikers still require medical attention in the canyon.
Some mistakes are common even among relatively knowledgeable hikers.
One is to not eat enough-during strenuous hikes, eating is just as important as drinking. Another is to let a surge of adrenalin carry you too far into the canyon during the easy hike down. Temperatures climb steadily as you descend, and the hike out can take twice as long. Another is not wearing adequate sun protection. Without sunscreen, a hat, and light-colored clothing on your skin, the heat can drain you even during the cooler months.