Health libraryBack to health library
The UV index: Numbers to know for sun protection
July 20, 2021—There's no doubt that the sun can feel awfully good sometimes, especially after a string of cloudy or rainy days. The problem with all that glorious sunshine, however, is that it can be dangerous to our skin—especially if we're exposed to too much of the ultraviolet (UV) radiation that's released from the sun.
One way to help protect our skin from the sun is to pay attention to the UV index.
What is the UV index?
It's a number found in the weather forecast that predicts the expected intensity of UV radiation from the sun. The numbers reflect how dangerous exposure to the sun is for that particular day, and they range from low (1–2) to extreme (11+).
Why is it important to know about UV radiation?
UV radiation interacts with the cells of our skin and even our eyes. Too much exposure can cause sunburn and, over time, premature aging. Repeated sun damage can lead to longer-term and more serious problems. These include skin cancer and cataracts. In fact, most cases of melanoma, the deadliest skin cancer, are caused by exposure to UV radiation over time.
What are the exposure categories in the UV index?
Low (1–2). This is the time when it's safest to be outside in the sunshine. But if you burn easily, cover up and wear a sunscreen of SPF 30 or higher.
Moderate (3–5). Wear sunscreen of SPF 30 or higher, a hat, and sunglasses.
High (6–7). Wear a wide-brimmed hat, sunglasses, and a sunscreen of SPF 30 or higher. Putting on a long-sleeved shirt and long pants, if practical, will help too. Seek shade during the midday hours of 10 a.m. to 4 p.m.
Very High (8–10). Cover yourself up as much as possible (with a wide-brimmed hat, sunglasses, a long-sleeved shirt and long pants). Wear sunscreen. Stay out of direct sunshine during midday.
Extreme (11+). Take every precaution available—wearing a shirt, pants, hat, sunscreen and sunglasses is a must. Stay in the shade as much as you can.
Note that the UV index can double if you are near reflective surfaces like snow and ice in the winter, beach sand in the summer, or bright surfaces anytime.
Where can you find the day's UV index?
Check weather forecasts wherever you usually find them: on the radio or TV news, on weather websites, in your local newspaper, or on smartphone weather apps. You can also put your ZIP code into the U.S. Environmental Protection Agency's website for your area's daily UV index forecast.
A little protection goes a long way
Following the UV index guidelines lets you enjoy the great outdoors while protecting yourself from sunburn and long-term damage to your skin and eyes.
Which strength sunscreen is best?
Learn more about which sun protection factor (SPF) level is best for different weather situations.
Subscribe to This Week in Health to get the latest health news delivered to your inbox.