This is a pictograph of a raindrop combined with some lines which portray a curtain of rain. The way in which the rain falls indicates that the wind is blowing from the south-west.
Illustrative Text Reference:
Kalibangan: Seal: K-18 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 302: Collections in India: Suomalainen Tiedeakatemia.
Image Credit:
Heavy Rain SW: Lynn Fawcett, 2017.