The 2010 climbing season is underway on Mount McKinley in Denali National Park & Preserve. This year, hundreds of climbers will test themselves against a 20,320-foot high behemoth that rates as one of the world's most challenging climbs.

Denali National Park & Preserve is a “climbers’ park.” Dozens of Alaska Range peaks in the park beckon to climbers, but most climbing activity is focused on Mount McKinley and to a lesser extent, Mount Foraker. Both are lofty peaks offering world-renowned, high-difficulty routes.

Denali -- the name by which Mount McKinley goes in the climbing community – is especially attractive because it is a very challenging 20,000-footer and great practice for Mount Everest climbs and other Himalayan expeditions. First climbed in 1913, Denali has become a magnet for mountaineers from all over the world.

By any measure, a Denali climb is a severe test of mountaineering skill and luck. Only about half of the climbers who make the attempt actually reach the summit, and most take more than two weeks to accomplish the feat. As of last year, 34,852 people were known to have made Denali climbs and only about 18,207 (52%) made it all the way to the top.

A total of 1,148 people registered for Denali climbs this season. Experience tells us that only around 600 can be expected to summit.

Lethally dangerous weather and treacherous glacier travel are Denali's signature features. It is known the world around as a killer mountain, and with good reason. Four climbers died on the mountain as recently as last year, and as many as 11 climbers have died on Denali during a single month (May 1992). Dozens of bodies lie unrecovered on the mountain, including one on the very summit.

Denali climbing has a sharply season rhythm. This mountain is heavily exposed (being close to the coast) and so high that it protrudes into the jet stream, yielding winter winds and cold so fierce that only the most intrepid mountaineers will venture onto the mountain when it is at its worst. Nearly everyone opts to make the attempt on the summit during the traditional climbing season, which extends from late April to mid-July.

Under ideal weather conditions (which do occur now and then), climbing Denali can be a lot easier and less logistically complicated than climbing other high profile mountains. Normal conditions, however, are quite another matter. About 75% of Denali climbers use the classic West Buttress approach to the summit, and West Buttress climbs take an average of about 18 days. Some of this time is used to pause at progressively higher elevations for acclimation to lower oxygen levels. The mountain’s weather being as lousy as it is, climbers also tend to spend a lot of time holed up in their tents and waiting out storms. Some may spend weeks doing that, eventually having to depart without ever getting a shot at the summit.

Weather and glacier conditions are the key considerations. Conditions usually ease significantly (becoming less miserable) by late April or early May, and that is when the narrow window of opportunity opens. Though some early arrivals can be expected during the last half of April, the rush to the mountain begins in earnest during May. June is the busiest month, with the largest number of successful climbs tending to occur in mid-June. As the climbing season wears on, warming temperatures yield increasingly dangerous climbing conditions (more frequent avalanches, riskier crevasse crossings, etc.) and pilots begin refusing to shuttle climbers from Talkeetna to the mountain's Kahiltna Glacier base camp (where the deteriorated glacial surface eventually poses unacceptable risks).

Of the 1,148 people who had registered for a Denali climb as of May 5 (see the Postscript), 130 were already on the mountain. None of the climbing parties had managed to summit by May 5, however, and four climbers had already abandoned the effort.

If you'd like more current information, the Talkeetna Ranger Station registration staff maintains a 24-hour mountaineering statistics line at (907)733-9127. A voice recording (updated daily) provides the number of registered climbers, the number of climbers currently on the mountain, and the total recorded summits. (The same information is also supplied for Mt. Foraker.) A summary of current climbing statistics is also available online at this site.

What climate warming portends for the Denali climbing season -- and for climbing conditions -- remains pretty much anybody's guess. However, in a typical year the climbing season has been over by early- or mid-July.

You can attempt a Denali climb outside the traditional climbing season, provided that you meet all of the Park Service requirements and are willing to begin your adventure with a very long trek (50+ miles from the nearest road), ascend further than the typical climber (an entire flank of the world's steepest-rising great mountain), and accept above-normal risks.

Postscript: The National Park Service regulates Denali climbing very strictly and provides or coordinates mountaineering services and programs that are difficult and expensive to maintain. Here is the gist of the NPS regulations:

All climbers attempting Mt. McKinley (20,320 feet) or Mt. Foraker (17,400 feet) must register with Denali National Park and Preserve. The strictly enforced 60-day pre-registration regulation allows mountaineering rangers to have direct contact with climbers before they arrive in Talkeetna. In doing so, rangers are able to suggest appropriate routes for different levels of expertise and offer first-hand knowledge of conditions encountered in the Alaska Range. Those attempting Mt. McKinley and Mt. Foraker must also pay a special use fee of $200.00 per climber, in addition to the park entrance fee ($10.00 per person or $20.00 per family). The special use fee offsets costs to the park related to mountaineering such as maintaining the high-altitude ranger camps, hiring seasonal staff, providing mountaineering booklets and information, and keeping the mountain environment clean.

The Denali National Park and Preserve Mountaineering Booklet, available in eight languages, covers mandatory requirements, search and rescue information, clean climbing ethics, high altitude medical issues, glacier hazards, and self-sufficiency. Climbers should have a solid understanding of the extreme mental and physical stresses associated with high altitude mountaineering.