The desert sun does more than just create a need for water.
Sunburn is easy to combat.
Use a sunscreen of at least SPF 15 and reapply it frequently. Pay particular attention to your nose, cheekbones, ears, and the nape of your neck. Sun-sensitive riders will want to take more extreme measures to blot out the sun. My experience has been that long sleeves are too hot and may lead to a second hazard, overheating. Heat exhaustion is a prominent danger here, especially in summer when temperatures above 100 degrees Fahrenheit are common.