Clouds are like signs of weather.

1. The phrase "clouds are like signs of weather" is used to illustrate that clouds in the sky are changeable and the weather is changeable. The meaning of "signboard" in the text is: the metaphor here indicates the change of weather.

2. The structure of this paragraph is: total score.

3. The last sentence of the article leads to the explanation center of the full text of the excerpt. In connection with the full text, the explanation center of the full text is: this paper describes the weather after the cloud changes, and emphasizes what kind of weather will appear when the cloud changes, thus highlighting the center.