Window of Opportunity: Everest Climbing Season Underway

By By Bill Deger, Meteorologist
March 26, 2013, 5:25:38 AM EDT

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For a few weeks each spring, the weather on Mount Everest improves just enough for adventurers to take the climb of a lifetime up the world's tallest mountain.

That opportunity is officially here, and from now through late May, hundreds of climbers will take advantage of this meteorological window that only about 3,000 others have before them.

Scaling the world's tallest mountain is certainly not for the faint of heart.

Despite the nearly calm weather conditions usually offered up during this timeframe, climbers always have to deal with extreme cold, avalanches, unstable ground and health difficulties as a result of increasing altitude and decreasing pressure.

But for these thrill seekers, it's now or wait until next year.

As Calm As It Gets

The summit of Everest at 29,029 feet (8,848 m) above sea level is high enough to penetrate the jet stream, a fast-moving "river of air" that can generate wind speeds of greater than 100 mph.

For a few weeks in May, the jet stream lifts north of the Himalayas, greatly reducing average wind speeds and the chance for precipitation at the top of the mountain.

This makes a trip to the summit more plausible than at any other time of the year, with climbers typically taking off during mid and late April to arrive at the summit just in time for the calmer conditions.

Climbers call the period of calm "The Weather Window."


The lift of the jet stream, enough to achieve the lighter wind, coincides with the beginning of monsoon season off the coasts of India and Sri Lanka, as winds begin to blow north from the Bay of Bengal.

By early June, the monsoon begins to blast the Himalayas with heavy snow. Because of this, the climbing season officially ends June 1 according to government-issued climbing permits.

A few daredevils often attempt to climb the mountain following the end of each monsoon season in September and October when the jet stream is once again temporarily displaced to the north.

However, autumn ascents are extremely difficult and even more dangerous since the climbing surface is often more unstable thanks to the copious amounts of fresh snow from the recent monsoon.

Still a Difficult Climb

While the exact numbers may never be known, more than 5,000 ascents have been made up Everest by more than 3,000 climbers since Sir Edmund Hillary and Tenzing Norgay became the first to successfully reach the summit in 1953.

More than 200 people have died during ascents, including two within the last week.


The recently deceased were Sherpas, the locals who call the mountainous regions of Nepal home. To climbers, they are immeasurably valuable guides and mountaineers.

Locals and seasoned climbers helped map two main routes up Everest, one originating from Nepal (along the southeast ridge) and the other from Tibet (along the north ridge).

An ascent up the southeast ridge is actually relatively manageable for many climbers. Freak storms, like the one that killed eight people over the course of just one day in 1996, are among the greatest dangers faced by climbers.

Meteorologist Evan Duffey points out, "Many expeditions rely on forecasts around three to seven days out for attempts at the summit."

"An accurate forecast will let a climber get to the summit and return without much delay."

Duffey adds, "However if a forecast is wrong, and a storm moves in while climbers are on the mountain, they can get delayed, or worse, trapped."

Another big danger is the often-deadly effects of high altitude on the body. Above 26,000 feet (8,000 m) climbers become dehydrated more quickly, often cannot sleep very well and face hypoxia, a lack of oxygen, and edema, a fatal buildup of bodily fluids.


This part of the mountain is often referred to as the "Death Zone," complete with temperatures around 30 degrees below zero and an atmospheric pressure that would render an unacclimated person unconscious in minutes.

In addition, most climbers require supplemental oxygen in the death zone.

Big Bucks for a Big Risk

Even if you make that tough decision to climb, you're going to need to fork over some serious cash.

Permits to climb Everest cost up to $25,000 a person. Add in the expenses of climbing gear, oxygen tanks, airplane trips and mountain guides and you may be looking at an expedition that costs more than the average annual income of an American household.

As those who have successfully climbed will tell you, the experience is a once in a lifetime thrill that will place you among an elite group of adventurers.

RELATED: Daily News and Updates from Everest Climbers

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