The last time hosseni described rain was when ali and Hassan left babas house. What is the significance of the rain in chapter 12?

 Rain often symbolizes change. It is a baptism into a new understanding of life. Baba does not want to undergo chemo for his cancer. It is raining and Amir is crying. Change is inevitable and Amir can feel it coming. There is regret, reconciliation, fear, and some peace in this rain.