Rare 'fire rainbow' spotted in Norfolk
Wednesday, February 5, 2014 - 6:23 am

“Fire rainbows” are not fire or a rainbow, but are commonly called it because of their brilliant pastel colors and flame like appearance. Technically they are known as circumhorizontal arc, which is an ice halo formed by hexagonal, plate-shaped ice crystals in high level cirrus clouds. The halo is so large that the arc appears parallel to the horizon, hence the name. The the sun must be at an elevation of 58° or greater, there must be high altitude cirrus clouds with plate-shaped ice crystals and sunlight has to enter the ice crystals at a specific angle in order to form a circumhorizontal arc. Photo submitted by Jill Vaquez, Norfolk.