Shutter
noun
A rain door is really just a shutter. In Japan, having shutters for rain protection is very common. When there were no glass windows, the shutters were simply like exterior doors in Japan, so "rain door" kind of makes sense as "shutter"!
This is a jukugo word, but it actually uses kun'yomi for both 雨 and 戸. Additionally, the reading for 雨 is actually slightly different from what you've learned, so here's a mnemonic to help you remember it:
Have you ever thought a shutter is like an armor (あま) for a window? They're both protections, and are usually made from metal. Kind of makes sense, right?
雨戸をリフォームする
to renovate a shutter
雨戸を叩く
to hit a shutter
雨戸を開ける
to open a shutter
毎朝、雨戸を開けます。
I open the shutters every morning.
最近は日本でも雨戸をつけている家が少なくなりました。
Recently, there are fewer houses with shutters in Japan.
雨が雨戸を叩く音で深夜に起きてしまった。
I woke up in the middle of the night because of the sound of rain hitting the shutters.