Q:

Is there a Portuguese expression for "raining cats and dogs"?

Supposedly, there are two origins for this expression:

One supposed origin is that the phrase derives from mythology. Dogs and wolves were attendants to Odin, the god of storms, and sailors associated them with rain. Witches, who often took the form of their familiars - cats, are supposed to have ridden the wind. Well, some evidence would be nice. There doesn't appear to be any to support this notion.

It has also been suggested that cats and dogs were washed from roofs during heavy weather.

So it always made me wonder, if in Portuguese people thought of a similar way to describe a heavy rain. Specially if it involves cats and dogs...

A:

The most similar expressions in Portuguese I can think of are:

chover a potes = "raining pots" (literally translated);
chover a cântaros = "raining jugfuls/pitchers" (also literally translated).

However, the intended meaning would be someone up in the sky pouring down water from big pots, or jugs full of it, repeatedly.
It seems Portuguese language was not influenced by those origins to describe a heavy rain as "cats and dogs" falling from the sky.

A:

Another expression used, at least in Brazil (as far as I know), is:

"chover canivetes"

which roughly translates to "raining pocket knives", or "raining penknives". This page (in portuguese) makes a quick discussion on "raining cats and dogs" vs "chovendo canivetes" vs "chovendo a cântaros" (as pointed in Armfoot's answer).

