“Raincoat” in Chinese is 雨衣 (yǔyī).
您最好穿一件雨衣。
You'd better put on a raincoat.
Example sentence from Tatoeba (CC BY 2.0).
Not to be confused with: 寓意 (yùyì, moral (of a story)) · 予以 (yǔyǐ, to give)