There are a few things you need to see a rainbow.
The main things are water droplets and sunlight.
The water droplets need to be illuminated by bright sunshine and they must also be in the right position relative to your eye sight.
A primary rainbow is always somewhere on an arc 42 degrees around the shadow of your head, which is called the anti solar point.
So the brightly illuminated water droplets must be in this direction away from you to see a rainbow.
For a secondary rainbow it is 51 degrees around the shadow of your head.
A rainbow is caused by the refraction and internal reflection of light inside rain drops, which results in the white sunlight being separated out into the colors of the rainbow.
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