For rain that has been falling to stop; the rain ceases (used to describe a change in the weather).
さっきまで降っていたが、今ようやく雨が上がった。
It was raining until a little while ago, but the rain has finally stopped now.
明日のピクニックは、朝になって雨が上がれば決行しましょう。
If the rain stops by morning, let's go ahead with tomorrow's picnic.
子どもが窓から『雨が上がったよ』と叫んだ。
The child shouted from the window, 'The rain's stopped!'