Several shallow lakes in Switzerland have frozen this winter, to the delight of hikers and skaters.
Lake Pfäffiker in the Zurich Oberland was the largest frozen body of water in Switzerland, attracting thousands of people eager for some slipping and sliding.
Lake Greifen and lowland lakes, such as Morat or Sempach, were watched carefully to determine whether they would be safe for pedestrians.
Zurich residents, too, were anxious to see whether their lake would freeze.
According to Patrick Hächler, a spokesman for the Swiss Meteorological Service, a lake can only freeze if there is no wind and temperatures plunge below -10°C. It must also have undergone a cooling period.
"A surprisingly large surface can freeze within just a few hours," Hächler explained. This was the case with the Lake Pfäffiker, where 12 cm of ice formed in a very short space of time.
In the southern canton of Ticino, temperatures have been too elevated for any ice to form on the lakes.
However, cantons Neuchâtel and Jura have been far more fortunate. Lake Joux and Lake Taillères have been frozen since the end of last year.
Residents close to Lake Geneva will not get the opportunity to see it frozen. According to Hächler, Europe's largest lake has not been covered with ice for the past 2,000 years, mainly because of its depth - approximately 250 metres.
People who are intending to walk or skate on a lake are advised to check whether the local authorities closely monitor the depth of the ice.
swissinfo with agencies
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