Weather idioms are common in English. What does 'It's raining cats and dogs' mean?

"It's raining cats and dogs" simply means it's raining very heavily, an idiom used to emphasize an intense downpour rather than describe anything literal about animals. Idioms like this work because their meaning has become fixed by convention over generations, completely detached from what the individual words would suggest if taken literally.

The idiom has nothing to do with actual cats and dogs fighting, and it certainly doesn't describe nice weather — both those readings interpret the phrase far too literally, missing the point that idioms must be learned as fixed units, not decoded word by word.

The exact origin of "raining cats and dogs" remains genuinely debated among etymologists, with theories ranging from old drainage systems washing dead animals into streets to Norse mythology, showing that even native speakers often use idioms confidently without knowing where they came from.