offer sacrifice for rain
雩 centers on a ritual act of offering sacrifice specifically to bring rain. Its meaning is narrow and tied to ancient ceremonial practice.
雩 combines 雨 (rain) with 亏, which is thought to represent a ritual implement or a phonetic element. The character likely originated as a depiction of a rain-making ceremony.
Rain 雨 falls on a ritual altar 亏: imagine a priest offering sacrifices under the rain to bring more rain.
For ウ, picture a priest chanting 'oooh' to the sky during the rain sacrifice: 'oooh' -> ウ, calling for rain.