Solar terms, what does beginning of autumn stand for?

Beginning of autumn is the 13 solar term in 24 solar terms, and beginning of autumn falls on August 8th or 9th every year. "Autumn" means that summer is cool, which means the beginning of autumn. When you arrive in beginning of autumn, the plane tree will definitely begin to shed its leaves, which is why there is an idiom "When you lose a leaf, you will know autumn". Literally, the word "autumn" consists of "valley" and "fire", indicating the maturity of five grains. Beginning of autumn is the first solar term in autumn, and autumn is a transitional season from hot to cold, and then from cold to cold.