Sunscreen should be applied about fifteen minutes before going out in the sun, and it should be reapplied every couple of hours. It is recommended to apply a sunscreen SPF 30 or higher. One ounce of sunscreen is considered the amount needed to cover the exposed areas of the body. Also, protective clothing such as hats with brims can help to reduce the risk of skin cancer. On a cloudy day, about 70 to 80 percent of ultraviolet radiation pierces the clouds, causing damage to the skin. Remember to wear sunscreen even on a cloudy day.