Avalanche! Skiers beware

British holidaymakers are arriving in Alpine ski resorts this weekend looking forward to spectacular mountain vistas, fresh powder snow and adrenalin-fuelled winter sports. They may not realise they are also heading into one of the worst avalanche seasons on record.

Forty-three people have died in the French Alps so far this season; last year, 25 died. Last week, 20 people, including a British man, died in France and Switzerland. On Friday, a skiing competition was wiped out in northern Italy.

A website which monitors off-piste conditions calls the recent period "the worst in living memory". This weekend, the avalanche risk in many resorts is classified as "extreme".

Since January, heavy snow has fallen across the region, creating the best skiing conditions for many seasons. But temperature fluctuations have also brought masses of snow cascading down mountains.

Betony Garner, of the Ski Club of Great Britain, said steep variations in temperature have made the snow very unstable. "At the start of the season it was relatively warm, but in January it got very cold very quickly, so the bottom layer of snow formed crystals that won't bond with other snow," she said. "If there's been a heavy snowfall people need to be very aware of the local avalanche risk."

Global warming has compounded the problem. Climatologists say rising temperatures have increased the rate at which glaciers and permafrost are melting, further destabilising steeper slopes. New snowfall creates an unstable top layer which, when dislodged, can sweep down at speeds of up to 160mph.

In January, an American skier died at the French resort of Courchevel when an avalanche caught him in full view of passengers on a chairlift. Despite an immediate search, he was buried for 20 minutes before his body was found.

Mountain guides warned that the risk of avalanches has been increased by the growing number of skiers and snow-boarders who venture off-piste in search of untracked snow. Hi-tech equipment now allows relatively inexperienced skiers to head off-piste before fresh snow has stabilised, putting themselves and others in danger. "It's amazing how stupid people are," Ms Garner said. "The avalanche risk is very high, but people still go off-piste without the right training and equipment." At least seven people were injured on Friday when an avalanche swept down on an international skiing competition in the western Italian Alps. Prosecutors are investigating whether it was triggered by skiers further up the mountain. This year, a British ski instructor was killed in Les Menuires when snowboarders apparently set off an avalanche above him.

Nicolas Sarkozy, the French Interior Minister, has called for a "zero tolerance" approach to skiers who endanger the lives of others.Authorities in the Alps have bylaws prohibiting off-piste skiing, but officials admit such regulations are impossible to enforce.

Ski resorts now hold regular safety classes and encourage avalanche awareness. Briton Suzie Vaill has been skiing for years, but only recently attended an avalanche safety talk on a trip to Verbier in Switzerland. "I had no idea I was putting myself in danger by going off-piste," she said. "I knew avalanches could happen, but I'd always imagined them higher up the mountains. I'm sure people don't realise the danger they're putting themselves in. But if you learn how, you can minimise the risk."

Mountain guides say anyone heading off-piste should carry a shovel, an avalanche probe and a transceiver to help rescuers find them if they are buried.

Ms Garner had a last word of warning. "When there's been lots of snow, it's not wise to go off-piste."