The sky as a horizontal line, a cloud hanging beneath it, and four drops falling in two columns. It is one of the most transparent pictographs in the language — three thousand years of writing reform and the rain is still visibly falling.
雨 sits on top of nearly all the weather: 雪 (snow), 雷 (thunder), 电 (lightning, in its traditional form 電), 雾 (fog), 需 (need — originally waiting out the rain). 下雨 is 'rain falls', and 风雨 (wind and rain) stands for hardship endured together.
The sky on top, a cloud below it, and four drops of RAIN falling inside.
Almost every weather word wears 雨 as a hat: 雪 snow, 雷 thunder, 雾 fog, 霜 frost. Look for the rain and you have found the forecast.