When the moon has a halo, a wind will arise; and when a column base turns wet, rain will come. Yun (晕) is a light circle around the sun or the moon, and chu (础) is a stone that serves as the foundation for a column in a building. This ancient proverb sheds light on the inevitable relationship between the “lunar halo”and “wind” and between the “wet column base” and “rain.” They speak to the wisdom of the ancient Chinese who learned to forecast weather through daily observations and repeated experiences. This proverb also contains the insightful realization that there exist necessary connections between certain things or phenomena. One thing or phenomenon signals the occurrence of another thing or phenomenon. Therefore, one can infer a certain thing or phenomenon from a given sign. Once people learn the internal rules governing changes, they can predict them based on their observation of the signs. As the Chinese sayings go, one is able to “tell the arrival of autumn by a falling leaf,” and “know the whole by its parts.”

All things have their inevitable trends, and all principles have their fundamental basis. Only those who are calm and cultivated can foretell from the faintest signs that significant changes are going to come. It is commonly known that a lunar halo forecasts wind and a wet column base rain. (Su Xun: On Detecting Wickedness)

A lunar halo forecasts wind and a wet column base rain. Things vary from one another in the world but their fundamental principles are the same. Only those who are observant can foretell significant changes to come by looking at the faint indications of an event or phenomenon. (Zhang Juzheng: Surviving Chapters on Strategies and Tactics)