Rain is liquid water in the form of droplets that have condensed from atmospheric water vapor and then precipitated—that is, become heavy enough to fall under gravity.
What is rain?
Water vapor from clouds condense onto a speck of dust till the weight makes it fall
Water droplets falling from the sky.
Rain is what happens when the good guys defeat the bad guys in the Lion King.
I couldn't actually tell you as it's been so long since it's rained here. The other answers will give you the info you need but I can hardly remember what it is anymore !
It's a rarity in Texas and a daily occurrence in the UK. (An English summer consists of a sunny afternoon with a shower of rain.)
But Europe has designated rain areas and, as Professor Henry Higgins informs us, "the rain in Spain stays mainly on the plain."