In my childhood, some winters were very cold. The lake in the background is situated right in the center of Hamburg, the "Alster", actually a river which was turned into a mill pond in medieval time. This photo was taken in 1955 or 1956, when I did a scientific research on the thickness of ice.
Then, in the mid-seventies, we had very warm winters, once on Christmas Eve 1977, it was 18° C/64°F. Now, we are going back to "normal" winters, it seems. Twice, at night, we had temperatures around -16° C/3,2° F.