When there were still houses with straw roofing, cats and dogs would catch some sun up there. When it rained, the roof would become slippery and they would often fall in front of windows. Someone was looking out the window when this happened one day and he exclaimed, "My! It's raining cats and dogs!"
The much more probable source of 'raining cats and dogs' is the prosaic fact that, in the filthy streets of 17th/18th century England, heavy rain would occasionally carry along dead animals and other debris. The animals didn't fall from the sky, but the sight of dead cats and dogs floating by in storms could well have caused the coining of this colourful phrase. Jonathan Swift described such an event in his satirical poem 'A Desc
Now in contiguous Drops the Flood comes down,
Threat'ning with Deluge this devoted Town.
Now from all Parts the swelling Kennels flow,
And bear their Trophies with them as they go:
Filth of all Hues and Odours seem to tell
What Street they sail'd 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 Confluent join'd at Snow-Hill Ridge,
Fall from the Conduit, prone to Holbourn-Bridge.
Sweeping from Butchers Stalls, Dung, Guts, and Blood,
Drown'd Puppies, stinking Sprats, all drench'd in Mud,
Dead Cats and Turnip-Tops come tumbling down the Flood.
We do know that the phrase was in use in a modified form in 1653, when Richard Brome's comedy The City Wit or The Woman Wears the Breeches referred to stormy weather with the line:
"It shall raine... Dogs and Polecats".
that was from this. http://www.phrases.org.uk/meanings/raining%20cats%20and%20dogs.html
I had heard the thatch roof thing a few times but it never made much sense. how did the dogs get on the roof for instance.
Years ago, the roof of the family home was made of Thatch. That is where the family animals slept because it was warm, over the fire. When the rain came long and hard enough, the thatch got slippery and the cats and dogs fell out. Hence it rained cats and dogs.
Raining animals is a rare meteorological phenomenon in which flightless animals "rain" from the sky.... the lightweight ones that are carried on the wind of a storm. The 'cats and dogs' part probably just originated there,and progressed to mean a heavy downpour.
I say it's a man-sized rain or a woman-sized rain.
From stepping in poodles