Klar wie Kloßbrühe

Literally: Clear as dumpling broth

Example: “Dass es heute regnet, ist klar wie Kloßbrühe.” — That it's going to rain today is clear as day.

English equivalent: Clear as day

Origin: Documented in use since at least the 1800s, confirmed by its appearance in the correspondence between the composer Carl Friedrich Zelter and Goethe, and two opposite-direction theories compete for its logic. One reaches back to "Klosterbrühe," a genuinely thin, clear monastery broth: monks and nuns preparing a simple fasting-season soup deliberately kept it free of solid ingredients specifically to avoid overindulgence, thin and transparent enough that the bottom of the bowl stayed visible straight through the liquid. A second, more likely theory reads the phrase as a deliberate joke built on the opposite: the broth left over from boiling German Klöße (dumplings) turns cloudy and milky rather than clear, so calling something "clear as dumpling broth" ironically claims total obviousness by comparing it to something that is, in reality, anything but clear.