Sun rays are more harsh during 10am to 4pm so most of the skin problems are caused by sun rays. The main reason for 90% of visible signs of aging is sun. The 80% of UVA and UVB rays can pass through clouds and penetrate skin easily. The best preventive methods is applying a sunscreen with an SPF 15 or higher. Sometimes reapplying after two hours is required after sweating and swimming. Another useful step to follow is 5 minutes of bathing, an optimum length saves body’s natural oils.

Source: graphs