The last line of the poem "Ode to the West Wind" is often quoted. "If Winter comes, can Spring be far behind?" What does this mean?

Melancholy, which is a salient characteristics of Romantic
Art, is a typical feature of Shelley's poetry. Ode to the West Wind is an impassioned
call to the abiding reality of nature wherein he implores it to blaze away things which
are dull and sick. He urges the Wild West Wind to Bring on the wind of
change.

The poem is divided into 5 stanzas, and
Shelley has finely distributed the roles on the West Wind in each of them. It has been
sometimes shown as the destroyer and sometimes as the preserver. Shelley himself has
been shown as somebody longing to share the brute force and the all-engulfing power of
the West Wind.

The last line "If Winter comes, can Spring
be far behind?" is the key to hope in this poem which is full and locked with ideas
pertaining to negativity although well-intentioned. Without this line, Shelley would
have been typecast as the "great-mourner" without a reason to mourn. [He was the
grandson of a rich country squire and had never experienced abstract poverty as Keats.]
 The 70 lines of the poem can be classified as the build up to the last two lines.
Shelley wanted to unleash the power of change and positivity onto the youths of his age,
[He was only 27 when he wrote this poem] and he chose the West Wind to carry his
message.

Autumnal decay and the barrenness of
winter may make the world desolate, but beyond lies waiting the Spring of another year.
It is this ebb and flow, the endless 'baffling change' of the great tide of humanity,
which Shelley sings, as well as the death and exit of dreary regenerative
seasons.

Shelley sings in exquisite melody of the advent
of millennium. Possessed by the creative principle, his dead thoughts become ashes and
sparks to feed a new conflagration. The poem ends on a note of hope and promise of
triumph.