Hi Gideon, constant rain represents constant blessings. Lightning in dreams and visions symbolizes God getting involved with things on the earth. It speaks of him getting active to intervene or to change or to do some very important work in the lives of people. It speaks of his majesty and power. The thunders and voices and earthquakes that are associated with lightning symbolize divine input that changes nations and it captures the attention and awe of people.
So this is wonderful. It is all about the blessings of God. However, it will be difficult to determine who this was all about. Is it about blessings in the life of your friend, or his family or his business, or his country? I do not know. He will have to determine what incident triggered his dream.