Seasons play an important role throughout the novel. They act as symbols and further connect the different parts of the story, making it very intricate.
In the first chapter of The Hobbit, when Bilbo Baggins takes off on an adventure, the action takes place sometime in April ("the firelight flickered—it was April—and still they played on," chapter 1). This starts the novel off in spring. Here, the season symbolizes new beginnings; Bilbo’s departure marks the beginning of a new adventure.
Later in the novel, while Bilbo—now accompanied by thirteen dwarves who requested his help with reclaiming their home, the Lonely Mountain—slowly makes his way to the destination, spring has already turned to autumn.
By the time they arrive at the entrance to the Lonely Mountain, Thorin Oakenshield remarks that autumn is nearly over. Here, the season symbolizes something sinister coming—as autumn is drawing to a close and winter is approaching, it foreshadows the inevitable Battle of Five Armies.