rain cats and dogs”可不是“下猫和狗”，引申为倾盆大雨。

【例句】
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。

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。