This poem, overladen as it is with Classical allusions, begins with a recognition of the dual nature of the wild, stormy, autumnal west wind and an appeal for it to hear the verses of the poet. It ends with the metaphoric appeal made by the poetic persona--or, in this case, the poet--that the wind's dual nature serve him. He asks that the wind drive out his "dead thoughts" in order to give "rebirth" to new thoughts just as seeds driven in the west wind give rebirth in the spring to new vegetation. He also asks that the wind drive his poetic words abroad to the world as words of inspired prophecy to an as yet "unawakened" (unenlightened) humanity.
The theme is that the tumultuous times and seasons of life have a dual nature since they enlivened poetic words that in turn, when spread throughout humanity, yield enlightenment and enlivened inspiration in those who read them.
In between, the persona describes the wind and its relationship of to "the dying year" while begging that the wind list to him: "O hear!" He compares the west wind to "locks of the approaching storm" and as the power that awakens the sleeping Mediterranean and makes it "grow grey with fear." Finally the poet says what he wants the wind to hear, which is that the wind bear him up like a "wave, a leaf, a cloud" because life has battered and because he has fallen on the "thorns of life!" He beseeches the wind to make him the wind's lyre, like the leaves are, and to imbue him with the "deep, Autumnal tone" so that the wind will be the poet's own spirit,
Be thou, Spirit fierce,
My spirit! Be thou me, impetuous one!
and in so being, drive out his "dead thoughts" so he can be renewed. All the way through, Shelley plays upon the dual nature of the wind (stormy destruction and scattering seeds of renewal) while he seeks to be cleansed then renewed: rid of his "dead" thoughts and the author of the "trumpet of prophecy."