One windy morning after a day of stormy weather, Christoph Geiss (Member 47,439) spotted a couple of layers of Altocumulus lenticularis above the summit of Mount Madison in New Hampshire, US. Lenticularis clouds can form when moist airstreams flow over raised ground like the mountains of New Hampshire and develop a rising and dipping flow downwind. The disc-shaped formations appear where the air cools most at the crests of these invisible, wavy airflows.

Their tiny, uniformly sized droplets diffracted the light as the Sun peeked from behind the summit ridge. This bent the paths of the light rays to create distinctive bands of pastel hues known as cloud iridescence.