Storms can arise quickly. If there's lightning, take cover - in a building, in your vehicle, or in a cliff dwelling if you're on the trail. Stay away from metal handrails.
Pace yourself. The Island Trail descends 185 feet (240 stairs) into the canyon. You will have to climb back up. The trail is steep and there are sharp dropoffs.
This is dry country. Fill your water bottle at the visitor center, and carry it with you. Keep extra water in your vehicle.
Speed limits are reduced for the protection of pedestrians and wildlife. Please watch for both.