Why is summer heat the most expensive thing among the 24 solar terms?

This is a sign that the weather is getting cold. Twenty-four solar terms originated in the Yellow River Basin, which is the crystallization of the long-term experience and wisdom of the ancient working people in China. Being in summer is a sign of cold weather, so it is the most expensive thing. It was originally formulated according to the shift of stars, and the ancients guided agricultural production according to the direction of the Big Dipper in the night sky.