The Long Night of Museums used to take place twice a year, once in the winter and once in the summer. As time went on, they turned it into an annual event that happens only every summer. As I spent a lot of time outdoors that night, watching food shows in the outdoor theater set up by the Gemäldegalerie and walking among the museums, it makes sense to me that they would switch to only having it in the summer. Berlin winters are very cold and dark, and the nights are particularly bitter, whereas the summers are warm and sunny, with very pleasant, cool evenings.
