Your Apple Watch now gives the most important skin advice you’ll ever get

When you first get your hands on an Apple Watch, it’s perfectly natural to feel bogged down by all the features. I mean, the heart-tracking metrics alone make my head spin. (Resting heart rate, who?) When it comes to protecting your skin though, there’s a number hiding in the face of the Apple Watch Series 5 that dermatologists really, really want you to pay attention to: the UV index.

“The UV index is a measure of the strength of [ultraviolet] rays reaching the surface of the earth at a particular time and location,” Joshua Zeichner, MD, a New York City-based dermatologist, previously told Well+Good. “The higher the UV index, the more powerful the UV rays are and the more likely our skin is to get sunburned.”

To find this metric in the wearable, search for a new watch face under the Face Gallery tab of the Watch app and look for the little sun icon with a number floating somewhere around it (or, you can simply check the weather app). Once you know the number, consult the World Health Organization (WHO) breakdown. It rates UV rays as follows: low (1-2), moderate (3-5), high (6-7), very high (8-10), and extreme (11 or more). Depending on the how high that number on your Apple Watch skyrockets, you’ll need to protect your largest organ in various different way (please see the cute chart below for details).

Obviously, you should be wearing sunscreen every day (rain or shine, low UV index or high). The number just gives you an idea of just how dire the need to slather on the SPF really is.

Still—look at you! You’ve now mastered how to use the UV index on Apple Watch. Please accept my congratulations (and that of a million derms, too).

Curious what sunscreen is the perfect match for your complexion? A derm has you covered:

These sunscreens were made for people with sensitive skin, and here are a couple more drugstore picks (for under $10!) that you don’t want to miss.