How fast a sunburn occurs depends on the ultraviolet index, but the range is about 10 to 60 minutes. Those people not using sun protection methods and with fair skin are likely to burn faster.
On a day with light clouds, approximately 80 percent of UV radiation can break through and cause a sunburn. Between the hours of 10 a.m. and 4 p.m. the sun's rays are the strongest, so the risk of burning is the highest. Those people spending time outdoors should always wear a minimum SPF 15 sunscreen that is broad spectrum, UV-blocking sunglasses. a hat and tightly woven clothing to protect against experiencing a sunburn, even on cloudy days.