Mountain climbing becomes much more complicated the higher that one has to go to get to the peak. Besides the normal dangers of climbing over rock, snow and ice, the loss of oxygen at the higher levels of a mountain and the neccessity of finding shelter in intense weather greatly adds to the challenges that a climber must face. Even experienced mountain climbers often have to turn back during a major climb as a result of difficult conditions, and indeed one of the hallmarks of an experienced climber is the ability to recognize when conditions have reached a point where it is too hazardous to venture further, and to make the choice to turn back even when significant effort has been expended to reach the current height.



The weather on the upper reaches of a mountain can be very dangerous, because snowfall can lead to whiteouts ' heavy blizzard conditions which make it next to impossible to see the surrounding area of the mountain. With greatly reduced visibility, climbers must be very careful to keep track of the distances that they travel and use a compass to gauge the direction that they are moving. Even someone familiar with a mountain may become lost during a whiteout ' it is essentially the same as traveling blind. Heavy snowfall conditions also make it more difficult for climbers to judge the other safety conditions of the surrounding area. Lightning storms can also be a danger as one ascends a mountain, as lightning is more likely to strike outcroppings or rock or people on the mountainside the farther upwards that one goes. When climbing a tall mountain, people will usually get started as early in the morning as they can to avoid the dangers of the weather, which usually intensifies at night or towards the end of the day.

Low temperatures are also an obvious danger the higher that one goes. Tents and sleeping bags with bivouacs provide some shelter from the cold and the wind, although tents may be noisy if they are constantly blown by the wind and the site must be carefully chosen so that the tent does not blow away. In some cases a climber will dig a snow cave ' this creates a quiet shelter in the side of the mountain which usually has a temperature of around freezing (this may seem low but it is sometimes better than what someone may get with a tent). Care must be taken in the building of the snow cave to make sure that it will not collapse as the climber sleeps.

Finally, mountain climbers must be careful of the hazards of oxygen loss. The higher that one climbs, the less oxygen there is in the air and the longer everything takes to do. Climbs which would be easy at lower altitudes require a much great effort as people become tired more quickly, and medical issues from lack of oxygen include headaches, problems sleeping, nausea, loss of appetite and general tiredness. If supplemental oxygen is carried, its levels must be constantly checked. Going without is more challenging, but may be safer if you can do it because you do not run the risk of dying from sudden loss if your oxygen runs out.