Why does it rain cats and dogs?

This expression as everyone knows means it is raining very heavily.

What we do not know precisely is the origin of this expression. There are, however, some explanations…

Firstly, let it be clear that there isn’t record of any incident of dogs and cats falling from the sky. It’s true that small animals like fish and frogs have been reported to have fallen from the sky, having been drawn skywards during hazardous weather. But cats and dogs, at least real cats and dogs…no record exists…

Also, the phrase seems to have little to do with the well-known hostility between dogs and cats, which is exemplified in the saying 'fight like a cat and dog'.

One of the most popular explanation is that cats and dogs, which lived in the thatched roofs of the traditional British homes, would have to leave their straw-shelter when it rained really hard. Thus it would rain cats and dogs!

It is also suggested that  a probable source of  the phrase 'raining cats and dogs' is that in the filthy streets of  old England, gutters could be awash with dead animals, heavy rain would frequently bring along dead animals, namely “cats and dogs”.  Though these animals didn't fall from the sky, the expression could have been coined from such a scene.

Jonathan Swift in his satirical poem 'A Description of a City Shower', first published in the 1710 collection of the Tatler magazine alludes to such a sight of water-borne animal corpses:

A Description of a City Shower(abridged)

(…) Now in contiguous drops the flood comes down,

Threatening with deluge this devoted town.

To shops in crowds the daggled females fly,

Pretend to cheapen goods, but nothing buy.

The Templar spruce, while every spout’s abroach,

Stays till ’tis fair, yet seems to call a coach.

The tucked-up sempstress walks with hasty strides,

While seams run down her oiled umbrella’s sides.

Here various kinds, by various fortunes led,

Commence acquaintance underneath a shed.

Triumphant Tories and desponding Whigs

Forget their feuds, and join to save their wigs.

Boxed in a chair the beau impatient sits,

While spouts run clattering o’er the roof by fits,

And ever and anon with frightful din

The leather sounds; he trembles from within.

So when Troy chairmen bore the wooden steed,

Pregnant with Greeks impatient to be freed

(Those bully Greeks, who, as the moderns do,

Instead of paying chairmen, run them through),

Laocoön struck the outside with his spear,

And each imprisoned hero quaked for fear.

Now from all parts the swelling kennels flow,

And bear their trophies with them as they go:

Filth of all hues and odors seem to tell

What street they sailed from, by their sight and smell.

They, as each torrent drives with rapid force,

From Smithfield or St. Pulchre’s shape their course,

And in huge confluence joined at Snow Hill ridge,

Fall from the conduit prone to Holborn Bridge.

Sweepings from butchers’ stalls, dung, guts, and blood,

Drowned puppies, stinking sprats, all drenched in mud,

Dead cats, and turnip tops, come tumbling down the floo

Swift alludes to swelling streets of filth of all colour and smell. All around the town “drowned puppies” and “dead cats” stunk and tumbled down the flooded streets.

Ilda Camarneira

Referências bibliográficas

The Phrase Finder (s/d). Raining cats and dogs. Disponível em http://www.phrases.org.uk/meanings/raining-cats-and-dogs.html

Oxford Dictionary Language Matters (s/d). Rain cats and dogs. Disponível em  http://www.oxforddictionaries.com/definition/english/rain-cats-and-dogs

The Guardian (s/d). Semantic Enigmas. Disponível emhttp://www.theguardian.com/notesandqueries/query/0,5753,-23990,00.html

Poetry Foundation (s/d). A Description of a city shower. Disponível em http://www.poetryfoundation.org/poem/180932