This is the link . Water should be uppermost in any traveler's mind. A hiker might dehydrate within hours.
Rangers recommend drinking at least a gallon of water a day.
Most backcountry emergencies occur on day hikes, so don't skimp on a short trail. Flash-flood season is July through September, though floods can occur every month. Check the weather at the park visitor center, which has the three-day forecast, and don't ask only about where you'll be hiking or driving. You should also inquire about the area upstream. And never camp, park, or drive a vehicle in a dry riverbed, a slot canyon, or a washed-out jeep trail.