On May 18, in the middle of Everest's spring climbing season, about 200 mountaineers, along with another 200 guides and Sherpas, began working their way to the top of the 29,028-foot peak. Some had planned to make the ascent the following day, but most had gone early when they heard the forecast: frigid, hurricane-force winds that could reach 80 miles per hour. A giant human conga line formed, snaking up an icy, perilous route. The result: four people dead – succumbing to exposure, cold, and lack of oxygen – placing that day among the most lethal on Everest since 1996, when eight people died in a massive storm.

Trudging through snow and ice on Everest's steep, narrow climbing path, in single file – the only way to climb or descend while safely clipped into a harness and rope line – the first group reached the summit at dawn on May 19. They soon started the long hike back down. When the climbers reached areas like the Balcony (a natural platform at 27,600 feet) and a ridge on the South Summit, the trouble began. Those descending had to wait, some for several hours, for those coming up to pass. Altitude sickness set in for Shriya Shah-Klorfine, a Nepalese-born Canadian, and South Korean Song Won-Bin. Cerebral edema (brain swelling) likely took the life of German climber Eberhard Schaaf. Veteran climber Jon Kedrowski saw Won-Bin. "He'd lost both mittens, and his hand was frozen in a clawlike fashion," he says. "Then he just looked at me, and his head went limp, and his eyes closed." Shah-Klorfine, he says, looked as if she had frozen to death on the rope line, her headlamp still lit. "I felt like, 'It's Into Thin Air [Jon Krakauer's account of the 1996 tragedy] all over again. I don't believe it.'"

A traffic problem, with potential for fatalities, has long been developing at Everest. Nepal and China used to limit the number of climbers on the mountain, but in 1993, both countries opened the doors to anyone who wanted to try to summit. The reasons were financial, particularly for Nepal, which charges guide companies a minimum of $25,000 per climber, pumping millions annually into its impoverished economy. "The Nepal government is greedy," says one experienced climber. "They'll take everything they can get."

Before Nepal and China changed their policies, you could count the number of people climbing Mount Everest at any point on two frostbitten hands. Ken Kamler, who's tackled the mountain six times, recalls a trip in 1995 when he was one of only nine climbers approaching the summit. "There was no issue of anyone ahead of us," he says. "There was no one around." Since 1993, however, the average number of annual attempts has risen to more than 200 – and roughly 3 percent of those people die. The number of people who reach the summit hasn't dipped below 100 since 1997, and it has been steadily rising ever since (see chart below). "It is astonishing and a bit horrifying to see people climbing cheek by jowl, packed together like that," says explorer and filmmaker David Breashears, who has made several movies about Everest.

There were brave moments: An Israeli man carried an ailing Turkish climber down the mountain, and a 73-year-old woman completed her first summit. But the fatalities overshadowed these feats for those in the business of leading hikers on Everest. "We're not bereft of clients," says author and veteran guide Robert Anderson. "As guides, we just hope every year we learn more about the danger factors. The fallout will happen when something much bigger happens, like when the ropes break. It's almost inevitable."

Himalayan Peak Rush
Nepal earns $25,000 for every climber permit, so don't expect these numbers to decrease. The surge has an environmental impact, too, with five tons of trash collected on Everest so far this year. Here are the numbers of climbers who reached the Everest summit, by year:
• 1989: 24
• 1993: 129
• 2000: 145
• 2005: 307
• 2010: 536