This poem, featuring the day of the poet's thirtieth birthday, apparently relates a walk from the docks up a nearby hill. However, as with all of the poetry of Thomas, this simple journey which gives the speaker ample time to describe the beauties of nature that surround him, is much more significant in terms of symbolism. The climb that he makes is shown to be an upward movement from birth, enjoying a life of "fond climates and sweet singers" before finally nearing the summit which is a "wonder of summer."
We can take this symbolism further by exploring the first three stanzas and how Thomas describes this part of his journey as "a springful of larks in a rolling / Cloud." This of course indicates the childish innocence of the early years of life before maturity and experience penetrate this world of wonder. Note how phrases such as "parables / Of sun light" and the description of "twice told fields of infancy" indicate the "truth of his joy" as he recalls the experience of youth and the simple joy of nature that such an experience involved.
It is in the fourth stanza, which represents a major turning point of the poem, that "the weather turned round." This change of the weather clearly points towards a more adult awareness of life and how this perspective impacts us. Note how the goal of the speaker is now just to keep the summit in sight. The change in weather indicates the passing of the seasons, and as we move from summer to autumn, it is clear that we are moving towards greater maturity in the poet's own life. The memories in this poem therefore allow the speaker to symbolically relive his childhood whilst also acknowledging that those days, the days of "a long dead child," are long past. Memories exist, but the poem acknowledges that only the approaching old age and death of humanity is what awaits us.