One of the reasons Denny is such a good driver is because of his skill in driving in the rain. Rain, he says, magnifies a driver's mistakes, and therefore many drivers fear the rain. However, when Denny explains the idea of manifesting one's destiny, Enzo comes to understand that rain is a symbol for strife, struggle, or opposition. Enzo sees Eve as his personal rain; he fears and resents her for the change she brought to his family, but by regarding her as a driver might regard the rain and as an obstacle to be overcome, he's able to improve their relationship. As an overarching symbol, rain symbolizes all the things that Denny must battle throughout the novel. Denny must fight first a sub-par crew and the demands of family, Eve's illness and then death, and finally a custody suit and a sexual harassment charge as he struggles to piece his life together and pursue a life as a professional driver. The use of rain in this way allows Enzo to further flesh out the theme of destiny and spirituality, as they rely fully on the driving metaphor to be understood. Denny is not considered just in terms of the man he is, but oftentimes more so in terms of the driver he is, which is one who is skilled at driving in the rain, and therefore able to overcome off-the-track obstacles to achieve his goals.
Rain Quotes in The Art of Racing in the Rain
I had always wanted to love Eve as Denny loved her, but I never had because I was afraid. She was my rain. She was my unpredictable element. She was my fear. But a racer should not be afraid of rain; a racer should embrace the rain.