The halo is so large that the arc appears parallel to the horizon, hence the name.
Brightly colored circumhorizontal arc occur mostly during the summer and between particular latitudes.
This is why circumhorizontal arc is such a rare phenomenon.
A colourful circumhorizon arc spans the sky near Fredericton, New Brunswick, Canada, in 2003.
The position of the observer is also important.
Circumhorizontal arcs cannot be seen in locations north of 55N or south of 55S.
Likewise there are certain times of the year when they are visible.
Circumhorizontal arcs should not be confused with Iridescent clouds, which can produce a similar effect.
If you love clouds, checkout this amusingcollection of shapes that clouds can take.
In this long-lens shot the halo forms a backdrop to a seemingly tiny aircraft.
Circumhorizon Arc in Alentejo, Portugal, 2006.
This peculiar ‘braided’ circumhorizon arc was possibly formed by plate crystals in high cirrus fibratus cloud.
Pictures taken at Silver City, New Mexico, USA during August 2004.
Circumhorizontal arc seen over Switzerland in June 2007
Circumhorizon arcs are often seen between lower obscuring clouds.
This one was seen in Redding, CA in June 2004.
