While hiking in Grand Staircase-Escalante National Monument park in southern Utah in search of hoodoos, I thought about the rainbow cloud I encountered in Death Valley. Rainbow clouds form because of cloud iridescence due to diffraction, a phenomenon that occurs when small water droplets or small ice crystals scatter the sun's light. Though rare, semi-transparent clouds or clouds that are just beginning to form are the ones most likely to be iridescent. I looked up and with good luck, I noticed a rainbow cloud at just the right time. It was fleeting and didn't last long. It pays to look UP!