It is a phrase not to be taken literally because of course there has never been any recorded incident in history where dogs and cats fell from the sky!!!

It is a phrase when one suggests it is raining very heavily...

Like thousands of other clishes, this phrase probably started somewhere with an original poem or story. Some great or lucky writer made this comment, which was once novel and fascinating, and for some reason it spread throughout English usage. "It's raining cats and dogs" is just one of those things people use to comfortably express something that seems to be happening. Heavy rain happens, and so people claw into their minds and chose a common answer, which is often the easiest course. It's just an illiteral e...

Like thousands of other clishes, this phrase probably started somewhere with an original poem or story. Some great or lucky writer made this comment, which was once novel and fascinating, and for some reason it spread throughout English usage. "It's raining cats and dogs" is just one of those things people use to comfortably express something that seems to be happening. Heavy rain happens, and so people claw into their minds and chose a common answer, which is often the easiest course. It's just an illiteral expression of the obvious; a simple view. People thrive around these universally fitting terms, and it's never neccessary to understand them completely; just knowing what one means is enough to justify them saying it.