Unlike UVA rays, UVB rays don't penetrate the deeper layers of your skin and usually result in sunburn. On the other hand, UVA rays feel a bit less intense but can reach the innermost layers of the skin, causing DNA damage inside the skin cells and, potentially, skin cancer. Also, UVA radiation is present throughout the year, even in winter and on cloudy days. For this reason, dermatologists advise wearing sunscreen throughout the year (especially on the face, hands, lips, and other parts of the body that aren't covered with clothing).