Clouds are like "signboards" of the weather. Whatever clouds hang in the sky will determine what kind of weather "signboard" will appear.

The original meaning of "signboard" refers to the sign hung in front of a store as a sign. The "signboard" here is an image metaphor, comparing clouds to the "signboard" of the weather. People can infer what the weather will be like in the future through various changes in clouds. So clouds are like the ‘signature’ of the weather.

. The explanation of "signboard" in Zhu Yongyi's article "Looking at the Clouds to Know the Weather": Ontology: cloud; Metaphor: signboard. Similarities: Both have indicative functions. However, the signboard is more obvious and close to life, making it easy for people to understand. Therefore, using a signboard as a metaphor is vivid and vivid. The word "signboard" uses a metaphorical rhetorical device here. Its original meaning refers to a sign hanging in front of a store with the name of the store or the goods for sale. As a sign of the store, it is used here to vividly illustrate the clouds and weather. close relationship.

The meaning of this sentence is that the appearance of clouds is closely related to changes in weather. By observing different forms of clouds in the sky, you can know what kind of weather there will be.