From deadly cold in Russia, floods in Britain and balmy conditions that have residents in southwest France rummaging for their bathing suits, the weather has gone haywire across Europe in the days leading up to Christmas.

The mercury in Moscow has fallen to minus 25 degrees Celsius (minus 13 degrees Fahrenheit) -- unseasonably cold in a country where such chills don't normally arrive until January or February.

The cold has claimed 90 lives in Russia since mid-December and 83 in Ukraine, with eastern Eurasia in the grips of an unusually icy month that has seen temperatures drop to as low as minus 50 degrees C in eastern Siberia.

Another 57 people have died from the cold in Poland this month, and officials say the icy front is probably "the most severe of the last 70 years," according to Regis Crepet, a forecaster with Meteo-Consult.

While the former Eastern bloc shivers and Britain fights severe flooding after heavy rains, holiday-makers and residents in the south of France and in Italy have dug out their shorts and swimwear to welcome an unexpected blast of beach weather.

Temperatures on Sunday climbed to 24.3 degrees C in Biarritz on the Atlantic coast, nearly 12 degrees hotter than the seasonal average, and nudging the 1983 record of 24.4 degrees C.

"These are remarkable temperatures that we do not see every year," French weather forecaster Patrick Galois said.

In Catania on Italy's Sicily coast, beach temperatures on Christmas day are forecast to climb as high as 22 degrees C in some places, while in Austria, the small village of Brand at an altitude of more than 1,000 metres (3,200 feet), noted a December 24 record of 17.7 degrees C.

Tim Palmer, professor of climate physics at Oxford University, told AFP the weather extremes are explained by the northern hemisphere "jet stream", a ribbon of air that speeds around the planet high up in the atmosphere.

The stream is akin to a length of rope "that you wiggle a bit", said Palmer -- its undulations differing from year to year.

This winter the jet stream is particularly wavy, pulling cold air in over Russia from the far north, and bringing hotter air up from the south over France and its neighbours.

"The question: Is the waviness and the unusual configuration of the jet stream the result of climate change? We don't know. The models are probably not quite good enough to tell us," said Palmer, though there was "some evidence" this may be the case.

"It is quite possible that carbon dioxide (being pumped into the atmosphere by human activity) is having the effect of making this jet stream waviness more intense," said the weather expert, but cautioned against apportioning premature blame for what may simply be localised weather glitches.

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