Colorado Skiing and SnowboardingLearn why Copper mountain is the perfect vacation destination for Colorado skiing and snowboarding - located close to Denver in the heart of Summit County. Why ski Colorado? Summit County, Colorado offers the longest ski season in the Western U.S. This season, Copper is open from November 6, 2010 through April 18, 2011. And Colorado is renowned for its sunny, blue-sky days along with some of the best powder in the world.