sky Spring is here—though here in San Francisco, especially these past couple of weeks, the fog has made it hard to tell!

Unfortunately, just because it’s overcast doesn’t mean you can’t get a sunburn while you’re out and about. Clouds do offer a tiny bit more protection than clear blue skies, but studies have show that even on the gloomiest of days up to 80 percent of the sun’s UV rays can make it through to you—and any time you expose your skin to UV rays, you’re risking skin damage.

Why is sunlight (whether you feel it or not) so damaging to your skin? When UV rays hit your skin, they create “free radicals,” atoms that damage your cells and make the collagen fibers in your skin—the stuff that keeps your skin elastic and youthful—break down. That’s why people who have spent too much time in the sun tend to have far more wrinkles than those who haven’t: they’ve destroyed the collagen in their skin through years of UV overload. And yes, plastic surgery offers a variety of anti-aging treatments to combat premature aging . . . but the best offense, as they say, is a good defense.

It can be tempting to skip the sunscreen when you look outside your window and see only grey skies, we know; but if you want to keep your skin looking youthful, covering up is your best option. So, that said, the next time you head out your door—regardless of what the weather’s like—slather on some SPF 30 (or higher, preferably) first!