Left and right parhelia with tails. The spots are situated on a line through the Sun parallel with the horizon. Parhelia frequently are very colorful. Hues of red lie toward the Sun. Fully developed, they have a long, white-blue tail extending away from the Sun parallel to the horizon.
Parhelia are sometimes so bright that observers are dazzled.
Parhelia are caused by flat, plate-shaped hexagonal ice prisms. If these plate crystals fall unimpaired, drag forces automatically orient them horizontally. The more the ice crystals are oriented horizontally, the brighter the parhelia appear to be. This phenomenon is observed when almost all the ice crystals are oriented horizontally, and few are oriented at other angles. There is an interesting relationship between parhelia and the circumzenith arc.