The weather in March is changeable.

The Monkey King Sun in the Journey to the West, after ten years of hard training and seven years of painstaking study, learned seventy-two changes, walking in clouds, doing somersaults and excelling in martial arts. He changed a lot on his way to learn Buddhist scriptures from Tang Priest and his disciples in the West, overcoming all kinds of difficulties and surrendering all kinds of demons. Because of his superb skills, later generations said that the Monkey King's face changed when he said it.

This two-part allegorical saying is now used to describe rapid changes. Just like the weather in summer, Wan Li is still clear and Wan Li in the morning, and thunder thunders and rain cats and dogs in the afternoon. It's really a monkey's face-it keeps changing.