I have this sentence.

It rains dogs and cats

It makes me crazy because I didn't know the meaning of it, until someone told me that it means "it rains a lot."

Now I have this sentence.

If we examine porpoises and dolphins at this level, they are as physically different as dogs and cats.

What does dogs and cats mean in this other sentence?

Is there any other usage of dogs and cats?

  • 1
    Raining cats and dogs is an idiom for rains a lot. When you want to contrast two things that are different, the usual English idiom is apples and oranges, but, in the sentence you cite, dogs and cats works better (no doubt chosen, as @mcalex said, because they are the most common household pets).
    – J.R.
    Commented Apr 15, 2013 at 10:50
  • Raining cats and dogs means it's heavy rain and thunderstorms
    – user25486
    Commented Oct 17, 2015 at 22:25
  • Another use is "lived together like cats and dogs" (alluding to the eternal struggle/competition between the canines and felines). Commented Oct 18, 2015 at 17:31

5 Answers 5


The expression is '... raining cats and dogs'. I have never heard of it raining dogs and cats.

But this is an expression, which a) is not meant to be taken literally and b) only holds when the 'cats and dogs' are taken as one (grouped) item

'... are as physically different as dogs and cats'.

In this sentence, the dogs and cats are not grouped, but are being referred to individually and separately. In addition, they are being referred to literally. In this context the phrase 'dogs and cats' is referring to two different four-legged, hairy mammals that people keep as pets.

The point the author is trying to make is that dolphins and porpoises (two very similar appearing animals) are actually quite different and that you should consider them as being as different to each other as much as you would consider dogs and cats as being different to each other. As @kojiro points out, in this context, the order of dogs and cats does not matter, yet as has been mentioned raining cats and dogs is always ordered cats, then dogs.

As an interesting aside, it seems other versions of it's raining ... for instance 'it's raining money', 'it's raining men', 'it's raining lawsuits', do refer to an abundance of the object - unlike raining cats and dogs - but the rain may be figurative. I suppose in that context - perhaps on entering an animal rescue shelter - you could say 'it's raining dogs and cats'.

  • 5
    It might be worth pointing out that the fact that the word order matters (cats and dogs, not dogs and cats) is a big clue that it's an idiom. …they are as physically different as (cats and dogs|dogs and cats) would be acceptable in either order.
    – kojiro
    Commented Apr 15, 2013 at 12:02
  • 25 votes up in 8 hours, wow...
    – NS.X.
    Commented Apr 15, 2013 at 19:20
  • 1
    “It’s raining cats and dogs” is an idiom, and also the first half of a joke: you follow it up by saying (or somebody responds) “I just stepped in a poodle” (pun for “puddle”). Commented Apr 15, 2013 at 23:48

First, the idiom is "It's raining cats and dogs!"

The answer to your first question is that cats and dogs are much bigger and heavier than normal raindrops, so the rain being described is much heavier than normal. It's not just "raining" but it's "super-raining" or "hyper-raining" or "ultra-raining".

Imagine a hailstorm with hailstones as large as baseballs: get hit by one and you'll probably die.

For the second question, dogs and cats are extremely different despite their being four-legged mammals that people keep as house pets. Porpoises and dolphins look like fish but are mammals, and, although to some people they might seem quite similar, they are actually as different as dogs and cats, the sentence says. I suppose the author might as well have said "as different as chickens and penguins" (both medium-sized essentially flightless birds) or "as sparrows and hummingbirds" (both very small birds), but most people are more familiar with cats and dogs than the other examples I gave because cats and dogs are ubiquitous (so are chickens) but sparrows, hummingbirds, and penguins aren't.

  • You forgot to explain the second usage... Commented Apr 15, 2013 at 13:42
  • 1
    @MikeB: I did it too fast and didn't notice the second one. Thank you for pointing that out. I'll add it, despite the fact that it's anticlimactic to do so at this point.
    – user264
    Commented Apr 15, 2013 at 14:36

Porpoises and dolphins are animals, dogs and cats are as well. The actual animals are meant in the context provided, because the text compares these animals.

A big clue whether or not real dogs and cats are meant is the part "it rains" in your first example. Dogs and cats don't suddenly rain from the sky, so it is used in the figurative sense in your first example

  • 1
    No. "Raining cats and dogs" is an idiom; see mcalex's answer. Commented Apr 15, 2013 at 19:42

My two cents:

While other answers talk about what is that idiom, I had read somewhere (not sure where) that it came from the practical observation many years back.

When it rained heavily, the cats and dogs walking on the roof then started falling down. These animals generally don't fall (as they have a perfect grip while walking), but then the rains were so heavy, they would lose their balance and start falling from the roofs. That's why it came from as a metaphor that it rains so heavily that cats and dogs will fall if they are on the roofs.


The verb "to rain" can be transitive. "To rain X" basically means that "X is falling out of the sky", whatever X is.

For instance, "On Saturn's moon Titan, it rains methane."

"Raining cats and dogs" literally means that small animals are falling out of the sky. But, of course, this image of animals falling from the sky is a metaphor for very large, heavy drops of water (and possibly dark skies, since animals are opaque).

The phrase is not an idiom, as the other answers misinform you. An idiom occurs when some piece of bad grammar is given an accepted meaning ("catch as catch can"), or when some sentence or phrase is given a completely different meaning from what it appears to say at face value ("kick the bucket").

"A and B are as different as X and Y" means that A is different from B, and this situation between A and B is similar to the situation between X and Y, which are also different from each other. The differences between A and B can be similar or parallel to those between X and Y, or they might not be. If A and B are very similar, then we actually expect X and Y to be similar.


"Classical music and grunge rock are as different as day and night". In this case, we learn nothing from the analogy, except that the speaker feels very strongly about how different those two kinds of music are. Two kinds of music are different in ways that do not really correspond to the differences between day and night.

"Porpoises and dolphins are as different as cats and dogs". Here, porpoises and dolphins are actually similar, but they have differences. Cats and dogs are also similar, and have differences. Those differences are somewhat parallel to those between porpoises and dolphins.

  • 1
    It is an idiom. An idiom is a phrase used where the meaning cannot be deduced simply by knowing the meaning of the individual words. The meaning is "heavy rain" not "cats and dogs falling from the sky".
    – Matt Ellen
    Commented May 1, 2013 at 8:27
  • An idiom is a phrase whose meaning cannot be deduced, period. If you said, "it is raining cats and dogs", you would be understood even if you were the first person ever to use it. "It is raining cats and dogs" is understandable in a way that "Joe bought the farm" isn't.
    – Kaz
    Commented May 1, 2013 at 13:41
  • No, Kaz, that is not what idiom means
    – Matt Ellen
    Commented May 2, 2013 at 9:14
  • My point in the previous comment was that a metaphor like "raining cats and dogs" doesn't have to be established by usage in order to be understood.
    – Kaz
    Commented May 2, 2013 at 14:55
  • If your point is that no metaphoric use of words can ever be anything other than an idiom, you're certainly entitled to your opinion; just don't expect everyone to find it enlightened. Speaking of which, the existence of enlightenment is why see the light isn't really an idiom. Light is an established metaphor for truth, wisdom and learning, and appears in other phrases like shed a light on something. Phrases involving light are not just canned idioms. It's a very poor choice of example in that OED entry. In the end, the OED is just a set of opinions, not all of them very good.
    – Kaz
    Commented May 2, 2013 at 15:17

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