Climb Mount Rainier (June 2015)
Credit: Tyler Stableford / Getty Images

Just because you've bagged a few peaks in the 12,000-14,000-foot range doesn't mean you're ready to march into the death zone (26,000 feet and higher). "You need to practice climbing on snow and ice," says Whittaker. And 14,411-foot Rainier has plenty of it; in fact it's the most glaciated peak in the lower 48. "It's got everything: nasty weather, snow and ice, and high altitude," says mountaineering god Ed Viesturs. On Rainier you'll carry a 35-pound pack stuffed with a minus-20-degree sleeping bag, crampons, and climbing rope, to name just a few items. And you'll log some serious vertical: 18,000 feet round-trip, over 30 to 36 hours. "You may sleep for two or three hours at the high camp at 10,000 feet," says Whittaker, "but most climbers don't." This is your first real test piece for Everest. You'll be dehydrated, nauseated, insufferably cold, irritable, terrified, and anxious. "Embrace suffering," says Whittaker. "It only gets worse after Rainier." [More information: RMI’s four-day climb, including instruction, costs $970; rmiguides.com.]