曇る
くもる · kumoru · JLPT N5 · verb-godan
to become cloudy
☁️ 曇 = sun 日 over cloud 雲; kumo (cloud) + ru = to cloud over
The kanji stacks 日 (sun) on top of 雲 (cloud): the sun is covered. The reading is just kumo (雲, cloud) turned into a verb with -ru, so kumoru literally means to cloud. It also covers glass fogging up or a face growing dim.