Why does it rain every solar term?

Where does the solar term come from? It is the conclusion of countless ancestors' life observation and summary, which is closely related to agricultural production.

Before and after solar terms, the weather often changes, because solar terms serve agriculture. The most needed information for farming is sunny and rainy days.

Therefore, the ancestors wrote down the omen and approximate time of the weather change and combined it with the calendar in order to catch up with the farming season.