Iridescence: Peppermint Clouds Over the Rio Grande Valley

October 22, 2015

By Darla Sue

Iridescence in clouds over the Rio Grande Valley. Photos by Darla Sue Dollman.
Each day for five days last week conditions were right for iridescence on the clouds over the Rio Grande Valley in New Mexico and the skies looked like they were filled with peppermint candy. The colors were lovely–turquoise, pink, orange, violet. It was a beautiful way to end a cool, fall evening.
What is iridescence? According to the National Audubon Society’s Field Guide to Weather, iridescence is “colorful bands or patches that appear in clouds.” There is no better way to describe what appeared in the New Mexico skies. These bands are created by light diffracted by water droplets in altostratus and altocumulus clouds. It occurred so often this past week that when I stared up at the sky I could predict that we would have iridescence that day.
According to Dr. Ludlum, author of the field guide, iridescence can occur any time of year, but generally occurs in the winter and over the mountains. In this case it appeared each night over the western skies, and the mountains are to the east. As you may have figured out by now, New Mexico often breaks the weather rules!