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One of the factors that makes K2 so challenging is the sustained technical difficulty. It is sustained often described as a cone of ice and limestone, and has slopes of 45 degree angles or more. Climbers typically fix up to 2,500 meters of rope on the south side routes, and up to 5,000 meters of rope on the north ridge route. Because high-altitude porters are rarely employed, all of the work of carrying and setting the ropes and high camps must be done by the climbers themselves.
On Everest, there are typically 2 four or five day weather "windows" during the spring climbing season. Although K2 is almost impossible to climb without being caught in life-threatening weather, the best months to climb are June, July and August. The sudden storms are caused in part because the peak is so much higher than the mountains around it -- it juts up into the upper layers of the atmosphere and like a rock in a river can create eddies in the jet stream, with good weather on one side of the mountain, and life-threatening conditions on the other.
There are fourteen "8,000ers" – fourteen mountains above 8,000 meters high that of course represent the 14 highest points on planet Earth. The following list of statistics was provided in February, 2001 by Xavier Eguskitza, the renowned Basque chronicler of Himalayan climbing. Although K2 is listed 3rd in the rank of danger, this is factoring in the total number of deaths.
Mr. Eguskitza points out, "If we consider the number of deaths coming down from the summit, K2 is by far the most dangerous, about 3 times more so than Annapurna. The problem on K2 is that if you reach the top, your chances of returning are significantly reduced."
http://www.k2climb.net/expguide/surviving.htm