YOU SAID:

It's raining cat's an dog's

INTO JAPANESE

雨が降っている猫の犬

BACK INTO ENGLISH

It is raining cats dogs

INTO JAPANESE

激しく雨が降っている。

BACK INTO ENGLISH

It's raining cats and dogs.

INTO JAPANESE

バケツをひっくり返したような雨だ。

BACK INTO ENGLISH

It's raining cats and dogs.