If your shadow is shorter than you are, then the sun is bright enough to be of concern.
There are two types of ultraviolet rays that are generally not filtered out by the ozone layer, UVA and UVB.
UVA rays account for 95% of the solar radiation that reaches the earth. They penetrate the skin more deeply than UVB rays and can penetrate clouds and glass. They are the rays that cause the skin to tan and are present on the atmosphere with equal intensity year round. Tanning is actually an injury to the skin’s DNA. The skin tans in an attempt to prevent further DNA damage. UVA rays cause the skin to prematurely age and wrinkle and damage cells in the basal layer of the skin, where most skin cancers occur. They have been proven to contribute to the development of cancer.
UVB rays do not penetrate the skin as deeply as UVA rays. They damage the skin’s surface in the form of sunburns. Although they are always present in the atmosphere, they are strongest between April and October, from 10 am to 4 pm. UVB rays are mainly responsible for the development of skin cancer.
Everyone, regardless of skin color, should make sun protection part of their daily routine. Adolescence is an important time to establish sun safety behaviors that will become lifelong habits.
Sun protection should include seeking shade, covering up with clothing, including a wide brimmed hat and UV blocking sunglasses and wearing sunscreen with an SPF of 15 or higher every day.