The cold, wind, and sun in the winter can do as much damage, or more, than in the summer. Because, number one is that we're not expecting skin problems. It's cold, so we won't burn.
Skiers be especially careful.
The reflective power of the snow, the higher altitude, and the thinner atmosphere combine to really multiply the effect of the sun. Wear protective clothing. Avoid the strongest midday sun. Wear sunscreen 30 SPF or higher. Put it on every portion of skin that is not covered by clothing, including bald spots, part lines, under the chin, and on the ears.