Snow and strong winds have put on hold the autumn ascent of Mount Manaslu, where a record 493 foreign climbers are waiting at base camp for a break in the weather.

The rope-fixing team reached the 8,163-metre summit late on Thursday, opening the route for hundreds of climbers waiting to make their summit bids. But persistent snowfall since Friday evening has forced them to remain at base camp, with strong winds at higher elevations making conditions unfavourable for climbing.

“The weather is not favourable, but the question is how long it lasts,” said Abiral Rai, an IFMGA-certified guide at base camp. His team does not plan to attempt the summit during the first weather window, expected to close before September 25.

Renowned climber Gelje Sherpa, speaking in a video message from outside his tent at base camp, urged climbers to remain cautious and watch for possible avalanches.

“Some tents have collapsed under the snow,” he said, pointing out that there was even more snow at Camp I and Camp II, raising the risk of further damage to tents and avalanches.

Three days earlier, an avalanche above Camp III buried and swept away sections of the fixed rope, delaying the rope-fixing team's work.

The delays have also heightened concerns about congestion on the mountain. Photographs and videos circulating from recent acclimatisation rotations show long lines of climbers and guides on sections of the route.

The actual summit push, however, has yet to begin because of the weather, expedition operators said.

With 493 foreign climbers holding permits for Manaslu this autumn, the mountain is facing one of its busiest seasons. A similar number of high-altitude guides and support staff are also accompanying the expeditions.

The scale of the season has prompted warnings from some experienced climbers.

“Nepal endured catastrophic floods shortly after losing several of its celebrated climbers on Broad Peak,” Mingma Gyalje Sherpa, the renowned mountaineer and expedition leader known as Mingma G, wrote on social media. “Now, numerous climbers are attempting Manaslu, Dhaulagiri, and various other mountains. I hope everyone checks the weather forecast before planning any expedition.”

On August 26, a flash flood of ice, rock and mud swept down the Trishuli River, destroying everything in its path, causing billions of dollars in property damage and leaving more than 1,400 people dead and more than 5,000 still unaccounted for.

On July 30, Nepal lost 10 elite climbers, including renowned mountaineer Nirmal Purja, known as Nimsdai, in an avalanche on Broad Peak in Pakistan.

Snow is expected to continue at lower elevations until Sunday, while strong winds and poor conditions are forecast higher up, according to mountain forecasters.

The immediate weather has been influenced by a western disturbance. Forecasters are also watching a potentially more significant system developing over the Bay of Bengal between September 23 and 25.

Krishna Bhakta Manandhar, a veteran alpine meteorologist, said a severe cyclone developing over the bay could bring heavy snowfall to the Himalayas later this month, although its eventual impact would depend heavily on its track.

“Heavy snowfall is possible during this period, or there could be no effect at all, depending on its eventual track,” Manandhar told Everest Chronicle.

He cautioned against drawing firm conclusions before the cyclone has formed.

“The track of the cyclone may change,” he said. “There are still five to six days to see how it develops and moves.”

Manandhar said that even if a cyclone forms over the Bay of Bengal, it would not necessarily bring severe weather to Manaslu.

“It looks as if it might reach Bihar, but we have to observe its formation to say anything more accurately,” he said. “It may not affect the mountains at all. It depends on how it moves.”

The uncertainty matters on a mountain where a favourable summit window can last only a few days. Climbers must also contend with snow accumulating on the route and strong winds that can make movement above the higher camps difficult.

For now, the climbers remain at base camp, watching the weather and waiting for the mountain to offer them a way up.