Ernest Hemingway’s 1925 short story ‘Cat in the Rain’ touches upon a number of themes, but it touches upon them lightly, for the most part. As is often the case in his fiction, Hemingway lets a few spare details suggest the inner lives of his characters, with these mostly external details hinting at much larger themes and ideas.
Boredom.
Boredom is an important theme in the story, since it is one of the catalysts for the wife’s actions regarding the cat in the rain. The wife is bored, and her boredom is doubtless exacerbated by the rain, which limits her potential activities further. Her husband seems similarly lacking in occupation, and whiles away his time reading, though whether he is enjoying himself or simply passing the time until the rain subsides is difficult to determine.
Isolation and Loneliness.
‘Cat in the Rain’ is a literary exploration of how it is possible to be married and still feel alone and isolated. The wife is not old (she’s described as a ‘girl’ at many points in the story), and she and George have presumably not been married long. Yet she already seems to be more drawn to a random cat outside in the rain than she is to her husband. This sense of loneliness and longing is coupled with her location, on tour in Italy and far from home.
Alienation.
Hemingway opens ‘Cat in the Rain’ by telling us that the husband and wife are the only Americans staying in the hotel in the Italian town. The wife appears to feel out of place there, although she is fond of the man who runs the hotel.
There is also a suggestion that she is possibly alienated from George, her husband, since he appears to take little notice of her in the story, his one act of chivalry being to offer (rather listlessly and noncommittally, perhaps) to go outside and bring the cat in for her. Otherwise, 
he spends much of his time reading his book and ignoring his wife. The wife cuts a lonely figure, who turns to the cat for some companionship and for a ‘project’ to focus on, a creature to connect with, and something to give her life purpose and direction.
Marriage.
The marriage between George and ‘the American wife’ is not explored in any depth in this very short story, but enough hints are given to depict two people who are not, perhaps, as close as a married couple might wish to be, for the reasons outlined above.
The wife appears trapped and constricted by her life, including her marriage – and perhaps by being in Italy, too. She longs to change her life, in small ways – growing her hair long, or buying some new clothes – or in slightly bigger ways, such as getting a cat.
But critics have proposed that she is pregnant and slowly coming to terms with the changes going on inside her (note how she is described as being ‘small’ and ‘tight’ inside), and that the padrone of the hotel makes her feel ‘important’. Is this all a coded and oblique allusion to her new status as an expectant mother?
Disappointment.
When the wife fails to find the cat outside in the rain, she feels disappointed. This disappointment is mirrored by the Italian maid, whose face tightens when the wife speaks to her in English. The maid, then, is a kind of double of the wife, as they both appear to experience disappointment at this moment.
‘Cat in the Rain’ ends with the maid bringing the wife a cat, but given the detail we are told about this cat (that it’s tortoise-shell: why not mention this detail when the cat was mentioned before, if it’s the same cat on both occasions?), it’s possible to infer that it’s not the same cat as the one that the wife spotted outside and took a shine to. Hemingway ends the story before we can learn whether the wife is disappointed with this gift or not.
Longing or Wanting.
Are the wife’s various cravings – to change her hairstyle, get a cat, buy new clothes, and so on – signs of her being pregnant? It is natural for a woman to have such impulsive wishes when her body and her hormones are undergoing such drastic changes. Her longing for spring to arrive can be said to symbolise new life, and this, again, chimes with the idea that she is pregnant.
War.
The war monument which stands outside the hotel is mentioned several times in ‘Cat in the Rain’. In 1925, when Hemingway’s story was published, the memory of the First World War was still fresh, as it had ended just seven years earlier.
Whether the sense of dislocation between the wife and the husband, George, is down to the war – as it is in T. S. Eliot’s 1922 poem The Waste Land, where a wife and her husband, a war veteran, communicate without seeming to listen to each other – is hard to determine. But it is important that Hemingway foregrounds the war memorial, mentioning it several times in this story which is, largely, focused on the female character rather than her husband.