The phrase simply means raining extremely heavily — a proper downpour. It is one of the most recognised idioms in the English language and is used across many English-speaking countries.
Jonathan Swift used a version of the phrase in his 1738 work A Complete Collection of Polite and Ingenious Conversation: "I know Sir John will go, though he was sure it would rain cats and dogs." However, the English writer Richard Brome used a related phrase even earlier in his 1651 play The City Wit: "It shall raine... Dogs and Polecats."
Several theories exist, none definitively proven. The most colourful involves Norse mythology: the cat was associated with storms and rain (the goddess Freyja, linked to weather, was said to ride a chariot pulled by cats), while the dog was associated with Odin and storms, often depicted with wolves and wind. In this interpretation, a heavy storm literally brought cats and dogs.
A more prosaic theory holds that in 17th-century cities, drainage was poor and heavy rain would flood gutters and streets. Dead animals — including stray cats and dogs — would be swept through the streets in the aftermath of heavy storms, making it appear as though they had fallen from the sky. Writers of the era documented the grim spectacle of animal carcasses in flooded London streets.
A third theory suggests the phrase is a corruption of the Greek word cata doxa, meaning "contrary to experience or belief" — but linguists generally find this less convincing given the lack of documentary evidence.
Whatever its true origin, "raining cats and dogs" has been in common use for over 350 years. Similar expressions exist in other languages: in German, "Es regnet Schusterbuben" (it's raining cobbler's boys); in French, "il pleut des cordes" (it's raining ropes); in Portuguese, "está chovendo canivetes" (it's raining penknives).
The earliest known use of a similar phrase is in Richard Brome's 1651 play The City Wit. Jonathan Swift used the modern form in 1738. It has been in common use ever since.
Yes. The phrase is used throughout the English-speaking world, including the US, Australia, and Canada. It is one of the best-known English idioms internationally.