Following the extreme summer, the risk of early snow on warm ground
Keystone-SDA
After a scorching summer in 2026, early snowfall on ground that is still warm increases the risk of avalanches and pressure on permafrost, the WSL Institute for Snow and Avalanche Research says.
A thick, early snowpack insulates the ground and prevents it from cooling further, stated the WSL Institute for Snow and Avalanche Research (SLF), located in Davos. As a result, the snow remains wet on its underside.
“On a smooth surface, such as grass or rocky outcrops, the entire snowpack can then slide suddenly,” said Alec van Herwijnen, head of the Avalanche Formation and Dynamics research group at the SLF. Following extreme summers, this phenomenon can also occur on high-altitude north-facing slopes, which are usually less affected.
Long-term risks
The timing of snowfall also plays a key role in high-altitude permafrost – that is, soil that remains permanently frozen above an altitude of around 2,500 metres. If the snowpack becomes continuous early in the autumn, heat is then stored in the ground and can continue to penetrate deeper.
More
More
How climate change is threatening permafrost’s delicate balance
In permafrost, at depths of ten to 15 metres, temperatures are influenced by long-term changes at the surface. The decisive factor is the succession of warm years over the last decade, of which 2026 has been the peak so far.
The accumulation of hot summers has significantly warmed the permafrost, which can lead to the loss of ice in the ground and allow water to seep deep into the soil. The stability of mountain slopes is reduced, with a risk of landslides and rockfalls. If, on the other hand, snow arrives late and the ground has time to cool down, this can mitigate the effects of the scorching summer.
Challenges of artificial snowmaking
Snow was scarce this summer in many places, even at high altitudes. At the SLF research site on the Weissfluhjoch, 2,536 metres above Davos, there was no snow at all from July to September – a first in 90 years.
More
More
Thawing permafrost threatens half of Swiss mountain huts
This does not necessarily mean there will be a lack of snow this winter, but artificial snowmaking could prove a challenge for mid-mountain ski resorts. Will there be enough water in January and February 2027 to produce new snow reserves? During these months, resorts produce artificial snow to build up reserves for the period after the summer.
“Another important factor, which is often underestimated, is the water temperature,” said Fabian Wolfsperger, an expert in artificial snow and snow farming at the SLF. If the streams and lakes that feed the snow cannons and snow lances are too warm, the machines find it more difficult to produce snow from this water. And this affects cross-country ski trails.
Furthermore, current air temperatures are simply still too high for artificial snowmaking. Ideally, they should remain below -5C for an extended period.
+ How we produce news in English
Translated from French, reviewed by an English Department journalist.
