A moonbow (also known as a lunar rainbow or white rainbow) is a rainbow that occurs at night. Moonbows are relatively faint, due to the smaller amount of light from the Moon. As with rainbows, they are in the opposite part of the sky from the moon. Moonbows can also appear to encircle the Moon, as a result of moonlight reflected off of ice crystals in the atmosphere.
It is difficult to discern the rainbow colors due to the faint nature of a moonbow, so it often appears as a pale, white arc.
Moonbows are commonly reported in Yosemite National Park in the United States as a result of geyser steam and the numerous waterfalls in the area.