While rain drops do come in groups, rain itself is just rain, it doesn't come in groups.
Wet
In the rain was sung by The Dramatics...
it was from a movie called singing in the rain, it was sung by Gene Kelly
I believe the group was called Apollonia 6
Efe Pygmies
Blind Melon
I Can't Stand the Rain taken from a 1972 album of the same name by Ann Peebles. Later covered by a group called Eruption, and Tina Turner.
rain.... episodes 78, and the end of 87
dancing in the rain
Kandy Rain in week 1.
Water enters the group through absorption.
The fairy tale you are referring to is called "The Little Tailor." In the story, a tailor cleverly tricks a group of giants into sewing up a rain cloud that is causing constant rain in a town.