I've mentioned it before, in another thread, but it might be useful to repeat it here (since there still seem to be folks in denial about
the trend of rising (global) temperatures).
In the Netherlands we have a winter-tradition called the "Elf steden tocht" (the eleven cities tour):
https://en.wikipedia.org/wiki/Elfstedentocht .
It is a 200 km long tour with ice skates on natural ice (frozen canals and waterways), leading past 11 cities in one single day, in the Northern province of Friesland. It has been officially organized since 1909, although there are reports of it being done since 1760.
The event only takes place once a year, provided that the ice is thick enough (at least 15 centimeters thick along the entire course).
Here are the years that is was possible to do the run:
1909
1912
1917
1929
1933
1940
1941
1942
1947
1954
1956
1963
1985
1986
1997
So, this event is not linked to a specific date, but it just has to be cold enough during the winter to grow ice that's going to be thick enough, and then it's a go within 48 hours (and care is taken to reduce the flow of water, as part of our water-management). The frequency of being able to organize the event has gradually been going down.
Yet another demonstration of the effects of Global warming as witnessed in a local venue.