Climbing a fourteener? Congratulations. You’re having a true Colorado experience. Here’s what you need to know to make sure it’s also a good experience. Related: Everything you need to know about climbing your first fourteener Altitude sickness: It’s very capricious. It can strike the fittest person in your group, and it can strike veteran climbers who never had it before. “Also, it can hit people as low as 10,000 feet,” Wendell said.