Remember summer evenings lying in the grass looking up at the moon? I have done this so many times that, if I can remember, I can guess exactly where the moon will appear each night, once again, only if I choose to remember.
Fire rainbows are the rarest of all naturally occurring atmospheric phenomena. For a fire rainbow to occur, cirrus clouds must be feet in the air with the precise amount of ice crystals, and the sun must hit the clouds at 58 degrees. (a/k/a Sun Doggies)