Why does the narrator move the reader through a change of seasons from late summer to autumn and on to winter?

That image is particularly well chosen, for even in this opening Henry connects rain with an undesirable type of fertility that actually heralds death and destruction. In addition to pregnancy's equation with weaponry, rain makes the country "wet and brown and dead" and brings on the cholera; the dusty opening, on the other hand, is idyllic in its pastoral splendour...While fertile, wet April is "the cruelest month," cold, sterile "Winter kept us warm." Rain will become a prominent symbol in A Farewell to Arms (as well as being the last word of the novel), and it is important to note its ironic application: it is not an agent of fertility and creation, but rather of sterility and destruction.