Supernumeraries are extra bands, usually pale pink or green in color, that are often seen bordering the violet edge (inside) of the primary rainbow. They result from the interference of light rays emerging from water droplets in the same direction as that light which forms the primary.

Supernumeraries are seen most often near the top of the bow and their numbers and spacing can change from minute to minute. As raindrop size become smaller, several things happen: supernumeraries become more widely spaced, the primary bow broadens and the colors of the primary bow become less saturated.

As the size of the water drops continue to diminish, eventually, the rainbow changes into a cloudbow or a fogbow.

The most likely place to see a supernumerary bow is at the top of a bright primary rainbow.

Supernumerary bows are easy to create with a garden spray, partly because of the smaller drop size but also because the drop sizes are more even.

Supernumeraries forming on a secondary rainbow are extremely rare, but when conditions are right, they appear outside the secondary past the blue-violet area.