Gallery: Cloud Iridescence

The presence of colors in clouds that resemble oil films on puddles in the general region of the sun or moon is known as cloud iridescence. This phenomena is rather common and is most frequently seen in lenticular clouds, cirrus clouds, altocumulus, and cirrocumulus clouds. Although they can be rather vibrant, the colors are often pastel. The effect may be hard to see when it happens close to the sun since it is obscured by the glare. One can get around this by using their hand to shield the sun or by hiding it behind a building or tree. Dark glasses or looking at the sky reflected in a pool of water or a convex mirror are other tools.

It has a similar effect to irisation. Diffraction from individual tiny ice crystals or water droplets scattering light results in iridescent clouds. Larger ice crystals can form halos, which is a distinct phenomenon, but they do not produce iridescence.