The year Lake Zurich froze over
It's hard to imagine now, but it actually happened in the winter of 1963. Lake Zurich froze over entirely. The authorities opened the ice on 1 February, and the last public festival on the lake began.

Documentary on the Seegfrörni of 1963 and the first Zurich Seegfrörni Race (in German). NZZ / YouTube
‘Antenne’, a programme broadcast on 4 February 1963 on the "Seegfrörni" on Lake Zurich (in German). SRF