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What is the UV Index?

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What is the UV Index?

Summer is quickly approaching and with that comes the need to pay attention to the UV Index. Yes, we’re talking about that mysterious number you see every time you open your weather app. It’s listed there because it’s really important. Keep reading to find out why.

If you care about protecting your skin from the sun, you should know all about the UV Index. So what is the UV Index and why is the UV Index important? We’re answering all of that and more below.


The UV Index is a numbered scale from 1 (low) to 11+ (extremely high) that measures the expected risk of overexposure to the sun’s UV rays.

What is the UV index?

The UV Index is a numbered scale from 1 (low) to 11+ (extremely high) that measures the expected risk of overexposure to the sun’s UV rays––and this encompasses both UVB, burning, and UVA, aging, rays. The index has nothing to do with temperature, so that means it could be freezing outside and the UV Index could be on the higher side.

You may notice that your weather app assigns a corresponding color to a range of UV Index numbers, so let’s go over what those colors are and what they mean… Lower numbers (1-2) will be labeled green, which means there’s a low risk of getting UV damage; numbers 3-5 will be labeled yellow and that means there’s a moderate risk of UV damage; numbers 6-7 are orange, which means there’s a high risk of damage; higher numbers (8-10) are red and that means there’s a VERY high risk of damage. Finally, anything 11 and above is labeled purple, meaning your risk of experiencing UV damage is extreme.

How is the UV Index number determined for each day in each city?

The UV Index number is calculated by weather experts and is based on four things:

1. The thickness of the ozone layer in your area. This is detected through satellites.

2. How many clouds are covering your area (clouds can block some UVB rays, but not UVA rays).

3. The time of the year it is. While it’s true that you should always be wearing sunscreen 365 days a year (UVA rays, we’re looking at you), the sun is angled closer to the earth – specifically the Northern Hemisphere – during the summer, making it more powerful…and damage from UVB rays more prevalent.

4. The elevation of your area. Because the closer you are to the sun the more UV exposure you receive.

Why should I care about the UV Index number?

Exposure to UV radiation (the sun) is the biggest contributor to skin damage, and even worse, skin cancer. One in five Americans will develop skin cancer in their life. Even more, the sun is the number one cause of skin aging. So if you want to look good and be healthy, you should care about the UV Index!

How do I protect myself when the UV Index number is on the rise?

Whether the UV Index is 1 or 5, you should always wear a broad spectrum sunscreen of at least SPF 30. But when the UV Index is above 5, you’ll want to take extra precautions. When the UV Index is moderate to high, you’ll want to wear an adequate amount of a broad spectrum sunscreen with SPF 40 or 50, as well as keep your skin covered in sun protective clothing and stay in the shade as much as possible.


When the UV Index number is high (aka above 6), it would be best to layer your sunscreen––but again, we’re big fans of doing this on a daily basis, regardless of what the UV Index is. Here’s one way to do it… First, use one of our base sunscreens (Superscreen SPF 40 for drier skin, Zincscreen 100% Mineral Lotion SPF 40 for acne-prone or oilier skin) and then add one of our primers (Unseen Sunscreen SPF 40 for drier skin, 100% Mineral Matte Screen SPF 40 for oilier skin) on top to ensure you have the right amount of protection on. And don’t forget about your body! For a fast-absorbing, hydrating option, go for our Everyday Sunscreen SPF 50. For a highly blendable mineral option, try our new Play 100% Mineral Lotion SPF 50. Also, don’t forget to reapply! You should do this at least every two hours (or more frequently if the UV Index is high). Defense Refresh Setting Mist SPF 50 and 100% Mineral Invincible Setting Powder SPF 45 make this part of your SPF experience super easy.

If the UV Index hits 11+, then we really hate to say this, but we don’t suggest spending long periods of time hanging outside. But if you really must, then applying and reapplying SPF 50 generously and frequently is the way to go.


If you already check your weather app every morning, it doesn’t hurt to start paying attention the UV Index number and prepare accordingly.

So does this mean I should check the UV Index number every day?

If you already check your weather app every morning (join the club!), it doesn’t hurt to start paying attention the UV Index number and preparing accordingly. But if you’re just not down for that, you could get a good read on the day’s UV Index by using the shadow rule. Simply look at your shadow to get a good guess of what the UV Index is. The shorter your shadow, the higher the UV exposure!

+ Do you have more questions about the UV Index? Leave them below!

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