It is during this time when the flowers a re blooming, trees are full of leaves, the weather is warm, and it is generally thought of as an enjoyable time during the year. In the lines that follow he begins to show the differences between the person and a summer's day. Line 3 says that the rough winds of the summer can destroy the buds of the flowers, which are the undeveloped flower. So I interpret that as Shakespeare saying rough winds can "shake" the buds of the flowers but can never destroy the inside of the bud, which is where the true beauty lies. This person's inner beauty will never be destroyed. In the fourth line of the sonnet, Shakespeare says how summer is too short and how his lover's beauty does not end like this season does. In the following lines Shakespeare describes how sometimes summer gets too hot, and is often uncomfortable, and sometimes the sun can be dimmed by the clouds, turning the day gloomy. But his lover is always temperate and calm, never showing signs of discomfort, all characteristics of an inner beauty. Line 7, 8,9 has almost a direct meaning in saying that everything that is beautiful will lose its beauty in time, either by chance or nature's planned out course, (chance which makes beauty fade by something terrible happening) but you shall not. Meaning that everything is eventually going to grow old and get ugly, but he's saying to his lover that you might grow old and ugly, but your inner beauty will never lose its beauty either chance or nature's planned out course. Shakespeare goes on to end the sonnet by saying this person's beauty will never die. "As long as men can breathe, or eyes can see, so long lives this, and this gives life to thee." Shakespeare's only conclusion to such beauty is to make sure that this person's beauty will grow and live forever in the minds of people who read this sonnet. .
Sonnet 130 compares the person in the sonnet to a number of other beauties, but always against the person.