This particular chapter was layered with biblical allusion and symbolism. The chapter starts off with Yossarian drunk and picking a fight with Colonel Korn, while outside it's pouring rain. Rain signifying the cleansing him and his bombardiers receive. Captain Halfoat even willing says that they would all rather die drowning than die Flying. Flying is no longer a symbol of freedom, but one of death and dismay.
Near the end of the chapter Yossarian would want the rain to go on forever. Therefore he would like to be forever cleansed from all the death he and his squadron have surrounded themselves with. However, the rain stops signifying that they cannot be cleansed and have to continue to fight until they die.