WeatherWhys for February 14,2014 from accuweather.com

Despite it being winter, the sun's rays are strong enough to cause damage to your skin and eyes where snow is covering the ground. That is especially true during February and March when the sun angle is a little higher. The temperature of the air is not a factor. Instead, it is a matter of a double dose of solar radiation between the rays coming directly from the sun and the rays being reflected off the snow's surface.