Sunday, May 19, 2013

Fire Rainbows: A Rare Cloud Phenomenon

“Fire Rainbows” are neither fire, nor rainbows, but are so called because of their brilliant pastel colors and flame like appearance. Technically they are known as circumhorizontal arc - 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.

Brightly colored circumhorizontal arc occur mostly during the summer and between particular latitudes. When the sun is very high in the sky, sunlight entering flat, hexagon shaped ice crystals gets split into individual colors just like in a prism. The conditions required to form a “fire rainbow” is very precise – the sun has to 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. 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 55°N or south of 55°S. Likewise there are certain times of the year when they are visible. For example, in London, England the sun is only high enough for 140 hours between mid-May and late July. While in Los Angeles, the sun is higher than 58 degrees for 670 hours between late March and late September.

Circumhorizontal arcs should not be confused with Iridescent clouds, which can produce a similar effect. While circumhorizontal arc occur only in cirrus clouds, iridescence often occur in altocumulus, cirrocumulus clouds and lenticular clouds but very rarely in cirrus clouds.

If you love clouds, checkout this amusing collection of shapes that clouds can take.


Circumhorizon arcs are so large that sometimes we see only parts of them where they happen to 'light' fragments of cirrus cloud. Ed Johnson (site) captured this one on June 8, 2003 on Mount Baden-Powell, California


Circumhorizon arcs are so huge that their colours sometimes appear to be those of the sky itself rather than an ice crystal halo. In this long-lens shot the halo forms a backdrop to a seemingly tiny aircraft. Picture taken at Pilesgrove, New Jersey in July 22, 2007


This circumhorizon display was photographed through a polarized lens above Dublin, Ohio, in May 2009.


Circumhorizon Arc in Alentejo, Portugal, 2006.


Circumhorizontal arc in Scottsdale, Arizona in 2009


Cirrus fragments lit by a circumhorizon arc, Halifax, Nova Scotia, on 3rd July 2001 with the sun 66° high.


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.


Circumhorizontal arc in Spokane Valley in June 2006


Circumhorizontal arc seen in Spokane Washington State, in June 3, 2006 when the sun was 64° high

Photos via Atopics, APOD and Wikipedia


  1. Deadly! Nice chemtrail shots!

    1. exactly, they really think we're THAT stupid..

    2. Yes, you're stupid if you don't think ice crystals can scatter light in the SAME exact way that a rainbow is formed.


    3. I have seen one of these in Coguille, Oregon just last night

  2. Saw one on Wednesday just gone. Newark Notts

  3. lol. I love how they say its a rare Phenomenon when I just saw 3 form today a a few more in the past couple weeks. Im in PA

  4. I saw one if these today and was really freaked out cus I've never heard of one before!

    1. because we didn't have chemicals in the air before, now they are everywhere. Thank you Geo engineering for at least making our last days on this planet more colorful... smdh

  5. i saw one of those in Florida in 2001

  6. Beautiful !!!!! I have seen this phenomenon 4 or 5 times in my life. Always in Canada

  7. I just saw one today! In Jacksonville,Florida!!!

  8. I seen one a couple weeks ago in colorado springs co

  9. i just saw it yesterday afternoon at 4:00 in Ipil, Zamboanga Sibugay, Philippines

  10. My daughter spotted one today in Minnesota and I was able to take a picture!

  11. Saw one 5/30/2014 in Tennessee.

  12. Friend observed many of these near San Diego, Calif. yesterday. Posted pics on FB. If you would like to add to your library, contact me.

  13. Saw one yesterday in Sussex UK

  14. June 5 Salt Lake City UT USA

  15. Saw 2 yesterday in Yakima, WA USA?

  16. 2 sides of the arc today in Hampshire UK around 6 pm

  17. Seen and took a nice pic in Marysville, Wa on June 20th. First time in my life to learn about these. It was more exciting that my kids and niece got to see it also.


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