A sunburn is the painful redness and irritation your skin develops after spending too much time in direct sunlight without protection. When ultraviolet rays from the sun hit your skin for too long, they damage the outer layers of skin cells, causing them to become inflamed, hot to the touch, and sometimes even blistered.

You've probably experienced a sunburn if you've ever felt your skin turn pink or red after a day at the beach, noticed it felt tight and warm, or had it peel a few days later. Mild sunburns make your skin tender and uncomfortable, while severe ones can cause serious pain, fever, and may require medical attention.

Sunburns happen more quickly than most people expect. Fair-skinned people can burn in as little as 15 minutes of strong midday sun, though anyone of any skin tone can get sunburned. The damage occurs even on cloudy days, since ultraviolet rays can penetrate clouds.

People prevent sunburns by applying sunscreen, wearing protective clothing like hats and long sleeves, and seeking shade during the sun's strongest hours between 10 a.m. and 4 p.m. Beyond the immediate discomfort, repeated sunburns over a lifetime can cause serious skin damage, which is why lifeguards, outdoor workers, and smart beachgoers take sun protection seriously.