Water
The most critical factor for human survival is water. You can live for weeks without food, but only a few days without water. Always carry extra water with you, whether you are driving, hiking, biking, or riding. Desert heat can lead to dangerous dehydration very rapidly. If you become stranded, conserve your energy and water by traveling at night or during the cooler times of the day. Rest in the shade during the hottest periods. Most people need at least two gallons of water per day in the summer heat. It is a good idea to always keep a few gallons of extra water in your vehicle regardless of the weather or time of year. If you are backpacking, carry a water filter or water purification system since you may not find water that is safe to drink.