Taking the title in consideration, the reader understands this is a sonnet contained into a collection of poetry dedicated to a mysterious man, known as "the Fair Youth".
Analyzing the layout, you can understand this is a poetry arranged into four stanzas, three of them are tercets and the remaining one is a rhyming couplet. Thus, the intelligent reader concludes this is a sonnet that follows the Elizabethan model. Indeed, it presents a problem or a situation in the three tercets seen by different points of view, and, in the final couplet, it offers to the reader a possible conclusion.
The sonnet opens with an apparent dialogue between the speaking voice and "thee", which in the archaic English meant "you", and, in this context, alluded to the mysterious man. This is a rhetorical question, due to the fact that the speaking voice answers itself. All the positive aspects stressed in this poetry are related to him. He is more lovable and gratifying than the season of summer, which is shaken by wind gusts that makes this period less beautiful. The poem is built on this rhetoric question between summer, the most fruitful season often utilized to create a comparison with the youthful beauty, and the idealized vision oh Mr W. H.
Right from the start the poet uses the semantic field of nature through summer and its positive aspects. Even though,in the second quatrain he refers to some natural and characterizing element of summer, which are not the best ones. Owing to this choice, he continues the praise of the youth. Shakespeare also uses the comparative form of majority "more and more", making this more efficient. In lines 7 and 8 he presents the problem: " And every fair from fair sometimes declines, By chance, or nature's changing course, untrimm'd". Even if this mysterious man is really handsome, he is only a man. As a consequence of this, he will certainly die. At the end of this poetry, in the rhyming couplet, the poet presents a solution: he is going to write verses that will make him immortal and eternal. Thus, the reader can also find the semantic field of time, that by the time, becomes an obsessive problematic. It ranges from verbs to words: by, summer, May, too short, date, sometime, often, every, declines, more and more. The poet also appeals to the sense of sight with the metaphor "eye of heaven" (line 5), which outlines the sun (the eye of the sky) but, at the same time, refers to the paradise, which, following Dante Alighieri and the medieval opinion, was above earth, exactly in the sky.