cats and dogs直译猫和狗，实际上rain cats and dogs是指倾盆大雨、滂沱大雨。

【例句】
We were about to get home, when it began to rain cats and dogs.
我们快要到家了，这时候下起了倾盆大雨。

In the middle of the picnic it started to rain cats and dogs, and everybody got soaked.
野餐进行中，突然大雨倾盆，每个人身上都湿透了。