The speaker of the poem appeals to the West Wind to infuse him with a new spirit and a new power to spread his ideas. In order to invoke the West Wind, he lists a series of things the wind has done that illustrate its power: driving away the autumn leaves, placing seeds in the earth, bringing thunderstorms and the cyclical "death" of the natural world, and stirring up the seas and oceans.
The speaker wishes that the wind could affect him the way it does leaves and clouds and waves. Because it can’t, he asks the wind to play him like an instrument, bringing out his sadness in its own musical lament. Maybe the wind can even help him to send his ideas all over the world; even if they’re not powerful in their own right, his ideas might inspire others. The sad music that the wind will play on him will become a prophecy. The West Wind of autumn brings on a cold, barren period of winter, but isn’t winter always followed by a spring?