UV-A (long wave-length) doesn’t cause damage right away, but over time it gets down deep into the skin. UV-A eventually causes photoaging: wrinkles, sagging, and sometimes skin cancer.
UV-B (mid range wave-length), though not as abundant as UV-A, causes instant inflammation, sunburn, and can also lead to skin cancer.
Year round UV protection with sunscreen, no matter where we are in the world, is best.
Children are especially susceptible to UV damage. The World Health Organization states skin cancer rates later in life are directly correlated to the amount of UV exposure an individual experiences before the age of 18.