Personified Nature

From the beginning of the poem, the speaker tries to set up a contrast between the beloved and a summer’s day. He tries really hard to distinguish them, ultimately arguing that the beloved, unlike nature, will be saved by the force and permanence of his poetry. The thing is, the contrast doesn’t really work, since summer, if anything, seems much more eternal than the beloved. If being written about preserves immortality, then the summer ought to be immortal because the speaker’s writing about it as well. And then there’s the fact that summer actually is, in some sense, immortal, since it returns in full force every year.

• Line 1: This is a rhetorical question, as the speaker definitely doesn’t care how or whether we answer him, and it also introduces what will be the main metaphor of the poem, as the summer’s day will be discussed using concepts more literally applicable to the beloved than to summer itself.
• Line 2: "Temperate" is a pun, since it carries two important meanings here. When applied to the beloved, it means "showing moderation or self-restraint," but when applied to the summer’s day it means, "having mild temperatures."
• Lines 3-4: This is all personification here. Even if winds might really be able to "shake" things, and buds could be described as "darling," these are both words more often applied to human actions. The next line is a much more obvious case of personification, as summer can’t literally take out a lease on anything. Note also that this implies a metaphor of the weather as a rentable property. Also, the "darling buds" introduce an extended metaphor of plant life and the conditions needed to sustain life that runs through the rest of the poem
• Lines 5-6: There’s the apparent opposition here, in that sometimes the weather is too hot, and sometimes it’s too cold. But there’s also personification with "eye" and "complexion." What’s more, "complexion" doesn’t just mean the appearance of the face, but also had a second meaning in Shakespeare’s time, referring to someone’s general internal well-being. Note also that the plant life extended metaphor is continued in "shines" and "dimm’d," since plants need light in order to flourish.
• Line 9: Here the personification is inverted: instead of describing nature in human terms, the speaker is describing the beloved in the terms of nature, giving him or her an "eternal summer" which could not literally apply.
• Line 11: "Shade" makes for a continuation of the plant life extended metaphor, since if you’re a plant stuck in the shade, that’s some bad news. "Shade" is also a pun, because it can mean "ghost."
• Line 12: The plant life extended metaphor is completed, as the speaker finally points out a way that plants can "grow," instead of all of these problems they faced in previous lines of the poem. Now what is this way? Well, perhaps aside from suggesting poetry, "lines to time" could also conjure up an image of plants lined up in rows in a farm. In other words, plants need to be organized and cultivated by humans in order to survive. This works really well with the main theme in the rest of the poem: that the beloved needs to be organized and developed by the poet in order to survive.