Heavy snow and cold snap swept across France over the week, putting many regions on high alert about extreme weather and causing traffic delays and cancellations.

On Saturday, heavy snow, as expected, fell across the Ile-de-France region that includes Paris and the surrounding area, while many northern regions, notably Nord and Pas-de-Calais, also witnessed extraordinary snowfall.

The French national weather agency Meteo France has put nine provinces in the country on "orange" temperature alert, warning people of traffic difficulties.

Weather forecasters also warned of black ice in northern France that would make driving particularly dangerous.

Many drivers were stranded on highways due to the snow, which resulted in traffic jams and partial road blockade. No serious traffic accidents have been reported yet.

France's civil aviation authority estimated that some 20 percent of flights to and out of the Roissy Charles-de-Gaulle airport have been canceled due to the snow during the daytime on Saturday.

The roof of a building at the Flamanville nuclear power station in northern France partially collapsed under the weight of the snow overnight Friday, triggering concerns about nuclear security.

Thomas Houdre, a senior official with the French Nuclear Safety Authority (ASN), excluded the possibility of nuclear leak after the accident when inquired by Xinhua.

The building does not house any nuclear fuels, so the environment wouldn't be affected, Houdre told Xinhua.

Houdre said that so far no abnormity has been reported and investigators were performing necessary checks.

French meteorologist Frederic Nathan said the sweeping snows and freezing temperature were rare but not abnormal. When cold snap struck northern Europe, the southern part of Europe was experiencing a warmer winter, which was the so-called climate balance, he told Xinhua.

Officials in the French Alps meanwhile warned of the risk of avalanches on Sunday in ski stations already open because of the early snow. The danger would increase Monday with fresh snowfalls and a subsequent thaw.

The French weather agency predicted that the temperature will rise slightly in the country on Sunday, but snows and rains will continue to dominate most of the regions in France.