Though the amount of UV radiation to which you are exposed varies with the time of day, season, latitude, and altitude, it can also be increased depending on your immediate environment. Clouds actually provide little protection from UV rays, and clouds, water, white sand, concrete, and snow all reflect UV rays and increase exposure. Of course, exposure to the midday sun or for long periods of time is most damaging. The ozone layer shields the earth from the sun's harmful UV rays. Over the past ten years, scientists worldwide have recorded decreasing levels of ozone in the atmosphere.
Less ozone means that more UV radiation reaches earth, increasing the danger of sun damage.
Effects of Sun Sunburn. Overexposure to the sun can happen in just a few hours. A bad reaction includes tenderness, pain, swelling, and blistering, and may include fever, chills, and nausea. While there is no cure for sunburn, wet compresses, cool tub baths, and soothing lotions may help. If you have a bad burn, see your dermatologist.