The underlying rhythm of “Ode to the West Wind” is iambic pentameter, which means that, on average, each line consists of five iambic feet. (Recall that an iamb has a da-DUM rhythm, as in the word “to-day.”) The choice of iambic pentameter for an ode such as this is unsurprising and conventional. Indeed, it was arguably the most common meter of Shelley’s day. Its popularity stemmed primarily from its capacity to approximate the cadences of natural speech without lapsing too much into the lilting rhythms common in songs. The five-beat line had an intrinsically noble sound that served particularly well in poems with serious subject matter. The rhetorical effect of Shelley’s poem surely profits from the inherent nobility of this meter. However, it’s also important to note that “Ode to the West Wind” features an unusual amount of deviation from the underlying iambic rhythm. In fact, Shelley introduces so much variation into the meter that it’s often easy to lose a sense of the poem’s rhythm, which in turn makes it challenging to analyze.

To get a sense for the way Shelley both uses and deforms iambic pentameter, let’s look at the two stanzas that open the poem, beginning with the first (lines 1–3):

O wild / West Wind, / thou breath / of Aut- / umn’s be- / ing,
Thou, from / whose un- / seen pre- / sence the / leaves dead
Are dri- / ven, like ghosts / from an / en-chan- / ter flee- / ing

The opening line establishes an initial pattern of iambic rhythm. However, for some readers the iambic meter may be difficult to discern due to the heaviness of the first four syllables. Indeed, some readers might prefer to interpret the first two feet as spondees, with two stressed syllables each: “O wild / West Wind.” This ambiguity gives us our first hint at the poem’s metrical complexity. The next hint comes at the end of the line, which features an extra unstressed syllable. The second line then opens not with an iamb but with a trochee (stressed–unstressed). Two iambs follow, but then Shelley concludes the line with a pyrrhic (unstressed–unstressed) and another spondee. The third line features yet more variation, with an anapest (unstressed–unstressed–stressed).

By contrast to the metrical madness of the opening stanza, the second stanza is much more regularly iambic (lines 4–6):

Yell-ow, / and black, / and pale, / and hec- / tic red,
Pest-i- / lence-strick- / en mul-/ ti-tudes: / O thou,
Who char- / i-o-test / to their / dark win- / try bed

The first two lines both open with trochees, but otherwise each line follows a generally iambic rhythm. Only in the third line does Shelley introduce a serious variation, with another pairing of a pyrrhic and a spondee. The intensity of the metrical variation ebbs and flows in a similar way throughout the rest of the poem. Though this variation may introduce difficulty for the reader, the overall effect is to evoke the blustery disorder that always comes when the wind blows through.