Rain, especially heavy rain, is symbolic of truth coming to us a little at a time and washing away the lies and distortions of materialism and egotism.

“Rain signifies divine truth from heaven.” ~Swedenborg

Since evil is just ignorance of God and spiritual truth, exposure to divine truth removes evil. Water is always symbolic of truth, purity, and divine wisdom. The forty days and nights of rain for which Noah built an ark symbolize a period of gradual enlightenment as the rain/truth gradually washes away the evil/falsehood and one arrives on the mountaintop: a place of enlightenment. Baptism is also symbolic of this relationship of water or rain and truth. 
    In dream symbolism, rain can mean many things, but if you are a person who is seeking spiritual enlightenment, seeing yourself getting wet in rain or being flooded with rain probably symbolizes that truth is flowing to you and you will become enlightened if you don't block off the flow.