June 2026
The UV Index measures how strong the sun’s ultraviolet (UV) radiation is when you’re outdoors. It’s reported on a scale of 1 to 11+, where 1 means minimal exposure, and 11+ means extremely high exposure.
According to the U.S. Environmental Protection Agency (EPA), here’s what the UV Index means in terms of UV radiation exposure:
- Low Exposure: 1 to 2
- Moderate Exposure: 3 to 5
- High Exposure: 6 to 7
- Very High Exposure: 8 to 10
- Extreme Exposure: 11+
Too much UV radiation can be extremely damaging. It can lead to sunburn and even sun poisoning, and it can greatly increase your chances of developing skin cancer later in life.
Here’s how the UV Index matters, how to check it, and how to plan around it.
Why the UV Index matters
People often think they can predict their risk of sunburn and long-term sun damage based on the cloud cover and the temperature. But even on cloudy days, UV radiation can be high because clouds don’t necessarily block out all UV rays. And even on cooler days, the UV index can still be high depending on how sunny it is, the time of year, and your location.
How to check the UV Index
Most online weather reports will give you both the current UV index and the maximum UV index that’s forecasted for that day. (Different sites are set up differently, so you may need to poke around to find what you’re looking for.)
Some sites, like accuweather.com, will also give you the forecasted UV index by the hour. This can be especially helpful in planning your outdoor activities.
Why you should check the UV index before you go outside
To prevent sunburn and skin cancer, you need to make informed choices about when to go outside, what to wear, and whether to apply sunscreen. And it’s not just about what the conditions are like right now. Rather, it’s about what they will be like for the entire time you plan to be outside. And the most accurate predictor of how dangerous the sun’s UV rays will be is not the temperature or the cloud cover, but the UV index.
What to do if the UV Index isn’t low
If the forecasted UV exposure is “very high” or “extreme,” you may choose to shift your outdoor activities to a time of day when UV radiation is less intense. Or you may decide to opt for a shady walk in the woods instead of a walk on the beach or on city streets — or do your daily run on an indoor treadmill rather than outside.
The EPA recommends using a sunscreen with an SPF 15 or higher if the UV Index is 3 or higher. With a UV Index of 8 or higher, the EPA recommends adding extra protection (such as covering your skin with clothing and sunscreen and wearing a wide-brimmed hat and sunglasses) and seeking shade, if possible.
If you have a history of skin cancer, very fair skin, have a young child, are elderly, or know you are more sensitive to UV radiation, you should take extra precautions beyond what the EPA recommends.
Why snow sports are especially risky
Checking the UV Index before skiing is critical because it’s easy to miss just how strong the sun’s rays will be. Colder temperatures can mislead skiers about the strength of the sun’s rays, especially when skiing in the spring (when the sun’s rays are getting stronger).
Keep in mind that, when it comes to skiing, the true UV Index may be significantly higher than what’s reported for two reasons:
- Higher elevations have more UV exposure. The sun’s rays become stronger as you increase in elevation (about 2% higher for every 1,000 feet you go up). That’s because there is less of Earth’s atmosphere reflecting some of the sun’s rays back before they hit Earth.
- Snow is extremely reflective. Because snow is so white, it reflects 80% to 90% of the sunlight that hits it, while sand and water only reflect 15% and 10%, respectively. This reflectivity can lead to “underside burn,” where you end up with sunburn on places like your chin or around your nostrils. It can also contribute to snow blindness, where the fronts of your eyes get burned. Before skiing, be sure to apply sunscreen to every inch of exposed skin and wear ski goggles with strong protection against both UVA and UVB rays.
