The sun gives off ultraviolet rays known as ultraviolet A (UVA) rays, which age your skin, and ultraviolet B (UVB) rays, which burn and can cause problems like skin cancer.

UVA and UVB rays can penetrate through clouds and are even present when it's raining, which is one of the biggest reasons why slathering on the SPF in winter is essential.

White snow reflects the sun's ultraviolet rays even more than water. SunSmart claims the snow can bounce back up to 90% of UV rays, getting a double dose from the sky and ground.

Winter sports like skiing or snowboarding can get pretty sweaty, and perspiration causes the skin to absorb more UV radiation, making us even more susceptible to sun damage.

Falling snow can even wash away sunscreen, and harsh winds can render SPF less effective, so be sure to use waterproof sunscreen and reapply every two hours.

People who spend a lot of time indoors near windows may tend to get complacent with the sun without realizing how much damage it's doing to their skin.

Dr. Elizabeth Mullans explained to Fox News, "Not all glass is created equally. It is important to apply daily SPF 30 or higher because harmful UVA rays can penetrate windows."

While they may be fortunate to have access to the best skincare specialists, celebrities such as Kourtney Kardashian and Leah McSweeney also swear by using SPF all year.

Jennifer Garner says, "Start your day with it. Don't waste any time. You have to do it whether it's overcast […] or sunny. It's just gotta be part of your routine."