You will sunburn much easier on a ski trip than on a beach vacation. Being on top of a mountain puts you closer to the sun and the sun's damaging ultraviolet rays. Steamboat dermatologist Sandra Eivins says, "Every 1,000 feet in altitude, you will get 10 percent more sun exposure and less atmosphere to filter." That's why you always need to slap on some sunscreen or cover up all together. Make sure it is waterproof in case it is snowing.
Light is also reflected off of the snow which makes it twice as dangerous. Dr. Eivins says you can get double the exposure with the snow reflection. "You get it from above and you get it from below with the reflection." A bad sunburn can ruin a vacation.
Experienced mountaineers advise neophytes to keep their mouths closed while on snow, so that reflected sunlight does not burn the unprotected roof of the mouth. That seems like good advice, or maybe the old-timers just want to enjoy the mountains in silence unbroken by the chatter of the newbies.
Use sunblock 15 minutes before going outside. Reapply it during the day. Sunblocks are rated for their SPF, which means Sun Protection Factor. The number is the multiplier factor for the time that it takes for you to get burned. If you burn in 10 minutes unprotected, an SPF15 will give you 15 times 10 minutes of protection. Dr. Eivins adds, "Cover up, and don't rely on sunscreens because they are not perfect and allow too much sun through them." A neck gaiter or ski mask helps keep out the sun and it keeps you warm when you're blasting down the mountain.
It is not just your skin that can get burned. Always wear sunglasses or goggles because you can also burn your eyes.