Poets and other writers frequently use the seasons to evoke emotion.
The most common imagery associated with Spring is birth (or rebirth) and beginnings. The emotions associated with Spring are hope and joy.
The most common imagery associated with Summer is fruition, abundance, fullness, and warmth. And because Summer is hot it brings sultriness and laziness to mind.
The Fall symbolizes completion, endings, and impending change (for the worse). It is a time for reflection. The feeling associated with Fall is sadness because the ease of Summer is giving way to the harshness of Winter.
Winter symbolizes death, barrenness, and emptiness. The emotions associated with Winter are coldness, emptiness, and loneliness.
Of course, these are only a few of moods and symbols of each of the seasons. Look at the poems and sayings in this article and see how the authors used the seasons to evoke mood and emotion specific to each season.