In previous years, the ice cover on Lake Weissensee was 50 centimetres thick. But some areas are unlikely to freeze over this season.
ADVERTISEMENTWarmer-than-average winter temperatures in Austria are threatening ice cover on Lake Weissensee, one of the country's few natural ice surfaces that has a sufficiently thick ice cover this year for people to skate on.
The thickness and quality of the ice are checked each morning. Wind, rain or snow can quickly damage the lake's relatively thin covering. In some areas, it is no longer possible to clear the ice with heavy vehicles.
In previous years, the ice cover here was 50 centimetres thick. Now every millimetre counts.
On Friday, around one thousand people flocked to the ice as temperatures fell just below zero. But concern over the ice here remains particularly high because, from 21 January, the lake will play host to a Dutch speed skating event that has been held in Austria for over 30 years.
About 6,000 athletes are expected to attend the event.
Click on the video above to find out more.