Where the shape comes from
Drops falling from a cloud: the line at the top is the sky, the hooked frame beneath it the cloud, and the four dots inside the rain coming down. It caps everything that falls or forms in the air: 雪 snow, 雷 thunder, 零 a drop and hence zero, 需 what one waits out the rain for, 雾. The traditional 電 for lightning is filed here too, though the simplified 电 has lost the cloud.
汉字 filed under 雨
No published character on HSK Guide is filed under this radical yet. 汉字库.