NBC Bay Area viewer Halcyon Teed sent us pictures of these brilliantly colored clouds after spotting them during an art class at the Windy Hills Preserve in San Mateo County Monday.
At first look, it appears the colors are caused by the reflection of light in the ice crystals of cirrus clouds.
NBC Bay Area metereologists Jeff Ranieri and Rob Mayeda say they are most likely iridescent clouds, which show unusual colors vividly or a whole spectrum of colors simultaneously.