It's raining cats and dogs!

I remember high school English class about the idiom "it is raining cats and dogs", referring to heavy rain. We all laughed a lot at this expression, it was really a funny one. Well, today it has been raining cats and dogs and that's not funny at all. I do not like wintertime. But I do like to wake up to the sound of rain pouring down. I found a cool illustration of this cat and dog thing(Wikipedia).In Portugal, we do not have this expression. We usually say "Está a chover a potes.""Potes" are recipients. So nothing funny about our expression. In Brazil, they say "Está chovendo canivetes." "Canivetes" are penknives! Their expression is funnier than Portuguese expression! A killer, I say!