Navin Singh Kadka
BBC World Service
Clear skies, gentle winds, and panoramic views of the snowy peaks of the Himalayas - that's the autumn that climbers on Mount Everest have come to love.
But it seems she's started to change.
The monsoons now extend well into autumn, the traditional mountain tourism season, meteorologists say, making weather conditions more unpredictable.
In the past decade, at least one episode of extreme precipitation has been recorded every year.
The reason for this is the prolonged monsoons, which become quite dangerous in the mountains.
Last weekend, a blizzard left hundreds of tourists stranded near the east side of Everest during freezing temperatures at an altitude of more than 4.900 meters.
Nearly 600 climbers have been rescued, Chinese state media said.
One man lost his life due to hypothermia and altitude sickness, while the others were reportedly in good condition.
This happened on the Tibetan side, but something similar happened on the Nepalese side, where a South Korean climber died on Mera Peak.
This was learned much later, as communication links were affected by torrential rain and heavy snowfall.
Landslides and floods in the country have claimed about 60 lives over the past week, officials say.
This weather is highly unusual for October, "when we expect the skies to remain clear," said Riten Jangbu Sherpa, a mountain guide.
Mountaineers have increasingly found themselves in unexpected extreme weather conditions in recent years, he added.
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Frequent storms like this one "have disrupted mountaineering and climbing businesses," he added.
The monsoon season in northern India and Nepal usually lasts from June to mid-September, but that is no longer the case.
"Our data shows that most years in the past decade have had monsoons that lasted until the second week of October, which is definitely a change," said Arkana Shrestha, deputy director general of Nepal's Ministry of Hydrology and Meteorology.
More concerning are the heavy rainfall and snow that the end of this season brings, as was the case this time on October 4th and 5th.
"Damaging precipitation is on the way in a short period of time," says Shrestha.
High in the Himalayas, such extreme weather conditions bring blizzards and snowstorms, posing a huge risk to hiking, mountaineering and tourism.
On the first weekend of October, the weather conditions changed quite abruptly - the winds started blowing, the temperature plummeted, and visibility dropped drastically.
The path leading the hikers to the rest station was covered in snow and impassable.
On Cho Oyu, a mountain located between China and Nepal, a team of climbers on the 8.201-meter peak had to temporarily retreat because snow was falling all the time.
"They have now returned when the snow has stopped falling," said expedition guide Mingma Sherpa, whose team consisted of six members.
But for the climbers trapped near the east side of Everest, the return was much more difficult.
Some of them were struggling with hypothermia despite being well-dressed, they told the BBC.
Others said they didn't sleep for fear of being buried under snow that fell so heavily that they spent most of their time clearing it.
Everything could have ended tragically if there had not been a well-coordinated rescue, and yaks and horses were clearing the snow.
However, one mountaineer, who has climbed these mountains more than a dozen times, told the BBC that he had never "experienced weather conditions like this before."
The cause may be more moisture in the air due to the way the world is warming, scientists say.
This leads to torrential rains that fall frequently after long dry periods, unlike in the past when monsoon showers were evenly spaced over four months.
"The weather at this time of year has changed every year in recent years, we can't promise our clients anything."
"September and October used to be the peak season and the weather was mild, but these days we are seeing extreme weather conditions and a rapid drop in temperature," said Pasang, a tour guide in the Tibetan capital Lhasa.
Turbo monsuni
Weather experts say that monsoons in South Asia sometimes appear to have become stronger because they are increasingly coming into contact with other weather changes.
Low pressure originating from the Mediterranean region and traveling east carries cold air that brings rain and occasional snow to northern India, Pakistan, and Nepal.
But when it meets air that is warmer and more humid, which happens during the monsoon, the result can lead to more extreme weather conditions.
Simply put, western weather disturbances can "turbocharge the monsoon," says Akshay Deoras, a weather scientist at the University of Reading, UK.
The reason this happens more often is that these weather systems occur in the winter, between December and March in northern India and the Himalayas.
But now, meteorologists say, they are more likely to arrive earlier, during the monsoon and autumn.
Rain and snow in eastern Nepal, where Everest is located, also occurred in early October due to weather changes in the west, officials from the Nepal Meteorological Department said.
This triggered a low-pressure system (an integral part of the monsoon's end) from the Bay of Bengal, pushing clouds eastward when they should actually be moving westward, they added.
Scientists have also found that in a warming world, the interaction between the Western Disturbance and the monsoon produces another unusual result.
Warmer air pushes clouds higher, meaning these weather systems can now cross the Himalayas and reach Tibet and other areas that didn't get as much rain before.
Study published in the journal Nature in June shows that "a warmer climate and the interaction between the Western Disturbance and the Indian Monsoon are forcing the Qinghai-Tibetan Plateau to shift to a warmer and wetter climate."
The Tibetan Plateau has always been an area with a dry climate.
And scientists say that a warmer, wetter climate in Tibet could mean unstable weather and frequent snowstorms and blizzards.
"What has changed is the reliability of the patterns, we can't assume that weather conditions will behave the same from season to season," says Logan Talbot, head guide Alpenglow Expeditions which brings climbers to the Tibetan side of Everest every year.
"This means that real-time decision-making and experienced guides in the Himalayas have become even more important than before," he adds.
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