köken: From Kaiser (“emperor”) + Wetter (“weather”). Originally referred to the notion that the weather was usually sunny on the birthday of Austrian Emperor Franz Joseph I (reigned 1848–1916). In the German Empire, it also referred to the belief that there was sunny weather when Emperor Wilhelm II (reigned 1888–1918) appeared at open-air events.
Wir hatten ja damals Kaiserwetter an unserm Hochzeitstag.