The best way to prevent skin damage in any case is to avoid episodes of excessive sun exposure. The following are some specific guidelines:
Avoid exposure particularly during the hours of 10 AM to 4 PM when sunlight pours down 80% of its daily UV dose.
Avoid reflective surfaces, such as water, sand, concrete, and white-painted areas. (Clouds and haze are not protective, and in some cases may intensify UVB rays.)
Ultraviolet intensity depends on the angle of the sun, not heat or brightness. So the dangers are greater the closer to the summer-start date. For example, in the Northern Hemisphere, UV intensity in April (two months before summer starts) is equal to that in August (two months after summer begins).
The higher the altitude the quicker one sunburns. (One study suggested, for example, that an average complexion burns at six minutes at 11,000 feet at noon compared to 25 minutes at sea level in a temperate climate.)
Avoid sun lamps and tanning beds. They provide mostly UVA rays, and some experts believe that 15 to 30 minutes at a tanning salon are as dangerous as a day spent in the sun.