Dozens of ski resorts in France face having to turn off their snow cannons because of a drought that threatens to ruin tens of thousands of holidays.
The machines have proved vital in the northwestern Alps this season, artificially creating ski runs following weeks of unseasonably dry weather.
But they will be switched off at more than 50 resorts in the Haute-Savoie département if there is no snow by the weekend.
Experts said that last month was the driest December in Haute-Savoie for 135 years, with just 0.2mm of rain falling in Annecy.
And, last week, a number of resorts recorded their 50th day without natural snowfall.
Pierre Lambert, the head of the regional government, said: “This would be a first. We are in a situation of drought, to the point that without snow or rain by the end of [this] week I will be forced to make a drought stoppage.”
The ban would prohibit ski resorts from producing artificial snow using water from the mains network.
Water could still be used from mountain reservoirs but most are depleted after heavy use during the Christmas and new year holiday.
Serge Taboulot, head meteorologist for the northern Alps at Météo France, said: “This is an unprecedented drought. We have data from the 19th century in Annecy, and we have never seen such a situation before.”
On some slopes the snow cover was the worst for 20 years, he added.
Ninety per cent of French mountains were said to be affected after below-average snowfall since the summer.
Most of the worst-affected resorts are clustered in Portes du Soleil, one of the world’s largest continuous ski areas which includes Les Gets, Morzine and Châtel.
In Les Gets, where virtually all reservoir water has been used, the ban could create serious problems.
Nearby La Clusaz and Chamonix have no natural snow at village altitude and are heavily reliant on artificial snow.
Thousands of British skiers visit resorts at Portes du Soleil each season.
Charlie Harris, 24, from Glasgow, said: “Last week there were quite a few stones on the slopes in Avoriaz.”
The Ski Club of Great Britain describes the pistes in Les Gets, where 40 slopes are closed because of lack of snow, as “hard packed” with just 5cm of snow at the base of the resort.
“Modest” snowfalls are forecast for later this week in the French Alps.