Thanks to everyone who sent photos of a weather phenomenon today – “rainbow clouds” over West Seattle. Above, from an anonymous texter; below, from Thomas Bach at Alki:

And from Craig Page, looking toward Vashon:

As explained here, this is also referred to simply as “cloud iridescence” is caused by “diffraction (which) occurs when small water droplets or small ice crystals scatter the sun’s light. … The cloud must be thin and have lots of water droplets or ice crystals of about the same size. When that happens, the sun’s rays encounter just a few droplets at at time. For this reason, semi-transparent clouds or clouds that are just forming are the ones most likely to have iridescence.”