Why do rainbows appear when it rains?

Important for a rainbow to appear is not when the rain appears but where: you see a rainbow when unobstructed sun is shining from behind you, raindrops in front of you and the angle between you, the raindrops and the sun is 42 degrees. read more

A double rainbow forms if sunlight is passing through a thin stratum of clouds and a stratum of rains simultaneously then you can get two rainbows at a time. Some rainbows form as an arc or a semi circle and that is because rainbows are only partial part of a circle around the shadow of your head on which rainbows are seen. read more