godan verb (-ru), intransitive verb
clear up; become completely clear
Describes the sky or weather becoming perfectly clear, often after rain or clouds. Emphasizes a bright, cloudless state.
雨がやんで、空が晴れ上がった。
The rain stopped and the sky cleared up completely.
朝にはすっかり晴れ上がるだろう。
It will probably clear up completely by morning.