What do you mean "clouds are like signs of weather"?

Clouds are like "signboards" of weather, which means that you can know the weather by looking at them.

"signboard" is a sign hanging in front of a store, which indicates the name of the store or the variety of business, and is used as a sign of the store. People can see the nature and business content of the store at a glance from the signboard. Clouds have the same function. From people's long-term practical observation, what kind of weather will appear when they find out what clouds are hanging in the sky. Such as thin clouds in the sky, it is often a symbol of sunny weather; Those low and thick clouds are often a sign of rain and snow. In addition to the thickness and height of the cloud, its color and the time when these colors appear sooner or later will herald a certain trend change in the weather. Therefore, you can "see the clouds and know the sky."