It is clear from the title of this great short story and the way that seasons are referred to in the first section that the seasons are very important to the story and its theme. Note how the seasons are described and their impact on Dexter Fletcher:
Fall made him clinch his hands and tremble and repeat idiotic sentences to himself, and make brisk abrupt gestures of command to imaginary audiences and armies. October filled him with hope which November raised to a sort of ecstatic triumph, and in this mood the fleeting brilliant impressions of the summer at Sherry Island were ready grist to his mill.
Note how this shows that Dexter is sentimental, sensitive and romantic. The way that winter makes him "melancholy" and spring makes him "dismal" also hints that his "winter dreams" are doomed for failure in the coming of spring. Thus it is important to analyse the impact of the seasons on Dexter Fletcher and his "winter dreams," identifying the way that the coming of fall makes his dream seem more possible and spring strips away his hope.
The four seasons in F. Scott Fitzgerald's "Winter Dreams" are symbolic of the moods of Dexter Green and his fantasies and values. Winter is symbolic of dreams that are illusions; spring is symbolic of restlessness and change; summer is symbolic of passion; fall is symbolic of a decline in heated feelings.
Fitzgerald writes that Dexter Green experiences "profound melancholy" in winter:
When he crossed the hills the wind blew cold as misery, and if the sun were out he tramped with his eyes squinted up against the hard dimensionless glare.
It is in the winter that Dexter creates his short-sighted and illusory dreams that affect his declining to take a business course at the State university because his "musings on the rich" occupy his mind. Much like someone searching through the snow for some lost object, Dexter reaches out "for the best without knowing why he wanted it." He only knows that he wants Judy Jones.
In the summer when he plays golf at the Sherry Island Golf Club, Dexter encounters Judy and in the heat of his emotions, Dexter falls madly in love with her. With the approach of fall, the summer love affair with its passion is over, and Dexter begins to realize that he cannot have Judy. "He had to beat this into his mind but he convinced himself at last." He goes East in February intending to sell out his laundries and to settle in New York.
In the next spring he finds himself enlisting in the army because of the war and beginning a new life.
At the end of Fitzgerald's story, Dexter learns of Judy Jones and that she has lost her beauty. He cries because he has lost the "country of illusion" of his youth where "his winter dreams had flourished."
Consider also the idea that seasons are often symbolic for the life cycle---spring is our youth, summer is our young adulthood, autumn is our mature years, and winter is a time of old age.
Now see how Judy herself is associated with each of these seasons and the time period in Dexter's life.