A very cool scene in the skies east of the Denver area this morning. These iridescent clouds lingered for a long time and provided a diversion while I was waiting for critters. We actually had some at sunset last night as well. Cloud iridescence is caused by clouds (usually cirrus) that have small water droplets or ice crystals in them causing the light to be diffracted, or spread out. The phenomena is much like the rainbow colors seen with oil in water.