Examples:
"The weather was horrible on saturday.
It was raining cats and dogs all day."


"It's really awful weather outside.
It's windy and it's raining cats and dogs."



We use this idiom to say that it is (or was) raining VERY heavily.
You often hear British people say this, as it rains a lot in Britain.
It doesn't mean that cats and dogs are falling from the sky!

≪簡訳≫
このイディオムは、雨がかなり激しく振っている(いた)ときの表現として使います。
雨の多いイギリスでは、よく耳にするフレーズです。
猫や犬が空から落ちてくる、ということではないのです!