The wingèd seeds, where they lie cold and low, Each like a corpse within its grave, until Thine azure sister of the Spring shall blow
Her clarion o'er the dreaming earth, and fill [. . .] With living hues and odours plain and hill (5-10, 12)
The West Wind plants seeds in the ground in the autumn that will germinate next spring. But the seedbeds are like graves, the seeds are like corpses, and their transformation in the Spring is like the resurrection of bodies during the Apocalypse. The Spring wind even blows a "clarion" that reminds us of the Last Trumpet. So there are two kinds of transformation here: the cycle of the seasons, and the linear finality of the Apocalypse. Somehow, Shelley suggests, every spring seems like the end of the world.
there are spread On the blue surface of thine airy surge, Like the bright hair uplifted from the head
Of some fierce Mænad, even from the dim verge Of the horizon to the zenith's height, The locks of the approaching storm. (18-23)
Shelley introduces yet another kind of transformation into the poem – the breaking of an autumn storm. The entire world, from the sky’s edge to its center, seems affected by this storm, and we know that, whatever the transformation that’s coming actually is, it will be utterly complete and leave nothing unchanged.
Thou For whose path the Atlantic’s level powers
Cleave themselves into chasms, while far below The sea-blooms and the oozy woods which wear The sapless foliage of the ocean, know
Thy voice, and suddenly grow gray with fear, And tremble and despoil themselves (36-42)
The West Wind transforms things it touches directly, like the surface of the Atlantic Ocean, but also things that it touches indirectly or that it only affects in a very distant way, like the beds of kelp, seaweed, and other marine plants on the ocean floor.
O! lift me as a wave, a leaf, a cloud! I fall upon the thorns of life! I bleed! (53-54)
The transformation experienced by human beings in their lives is one of pain, suffering, and martyrdom – the "thorns of life" aren’t a direct Biblical reference, but they certainly imply a Biblical atmosphere by reminding us of the "crown of thorns."
Be thou, Spirit fierce, My spirit! Be thou me, impetuous one! (61-62)
The only transformation that the speaker believes can remedy the effects of the "thorns of life" is a complete fusion of Man and Nature, or maybe even a replacement of Man’s puny "spirit" with Nature’s immense "Spirit."