"Free flying flowers are as light as a dream, and endless rain is as fine as sorrow" refers to falling flowers dancing in the wind at night. The endless rain falling all over the sky is inextricably linked, just like the melancholy in this heart. The Song Dynasty poet Qin Guan's "Huanxisha Lonely Cold Building" compares the fallen flowers to a dream at night by metaphor.
I'm glad to answer your question. I hope it will be adopted.