Wisconsin residents stunned by rare 'fire rainbow'

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Wisconsin Residents Stunned by Rare Fire Rainbow

By Weather.com

You've all seen rainbows, but have you seen a rainbow in a stripe across the sky? That's what residents of western Wisconsin saw and photographed over the weekend.

What you see in the photos is called a "circumhorizontal arc" -- or CA -- or what appears to be a fragment of a rainbow.

Typically you associate rainbows with rain and sunlight. However, CAs result from the refraction of sunlight through plate-shaped ice crystals.

For a CA to form, the sun has to be 58 degrees above the horizon. This is a rare sight at higher latitudes, where the sun is not sufficiently high above the horizon. In the middle latitudes, however, the spring and summer months offer the best chance to see this.

CAs show up primarily where cirrus clouds are located. It's as if wispy cirrus clouds take on a rainbow palette.

Another variation of this is called a circumzenithal arc, which appears as a quarter-circle rainbow. For this to form, the sun has to be 5 to 32 degrees above the horizon. An angle of about 22 degrees above the horizon gives the optimal brightness, arc length and width for viewing. It will always be on the same side of the sky as the sun.

We would love to see your amazing photos of these phenomena. Share them with us either at weather.com/photos, or on Facebook, Twitter or Google+.

RELATED: See photos of Japan's lightning volcano:

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Wisconsin residents stunned by rare 'fire rainbow'
A volcano explodes into life as it sprays burning hot ash high into the air - followed by a deafening shockwave. Shot by filmmaker Marc Szeglat, 47, this incredible footage shows the highly active Sakurajima volcano on the Japanese island of Kyushu.
Volcanic Lightning during eruption at Sakurajima in Japan - 24 February 2013.
Volcanic Lightning during eruption at Sakurajima in Japan - February 2013
Volcanic Lightning during eruption at Sakurajima in Japan - February 2013
In this photo released by Kagoshima Local Meteorological Observatory, volcanic smoke billows from Mount Sakurajima in Kagoshima, on the southern Japanese main island of Kyushu Sunday, Aug. 18, 2013. Kyodo reported that it erupted Sunday evening, marking the 500th eruption this year at the 1,117 meters (3,686 foot) high mountain, which is one of Japan's most active volcanoes. There is no immediate reports of injuries. (AP Photo/Kagoshima Local Meteorological Observatory) CREDIT MANDATORY
In this photo released by Kagoshima Local Meteorological Observatory, volcanic smoke billows from Mount Sakurajima in Kagoshima, on the southern Japanese main island of Kyushu Sunday, Aug. 18, 2013. Kyodo reported that it erupted Sunday evening, marking the 500th eruption this year at the 1,117 meters (3,686 foot) high mountain, which is one of Japan's most active volcanoes. There is no immediate reports of injuries. (AP Photo/Kagoshima Local Meteorological Observatory) CREDIT MANDATORY
Black smoke billows from Mount Sakurajima on the southern Japanese main island of Kyushu as the volcano repeatedly erupts Saturday, Oct. 28, 1995. The Regional Meteorological Observatory issued an eruption warning in the region. (AP Photo/Kyodo News)
KAGOSHIMA, JAPAN - DECEMBER 09: (CHINA OUT, SOUTH KOREA OUT) A drone flies around the crator of Sakurajima, active volcano during a test on December 9, 2014 in Kagoshima, Japan. The test continues until December 11, aiming to put into practical use in three years to research crators of volcano eruptions which is too dangerous to approach. (Photo by The Asahi Shimbun via Getty Images)
Sakurajima volcano stands in Kagoshima, Japan, on Sunday, Oct. 26, 2014. Japans economy tumbled into its steepest contraction in more than five years after a 3 percentage point increase in the tax in April. Abe is weighing whether to go ahead with a hike to 10 percent next October, as legislated by the previous government. Photographer: Tomohiro Ohsumi/Bloomberg via Getty Images
Sakurajima volcano is seen from a ferry traveling in Kinkowan Bay, Kagoshima, Japan, on Sunday, Oct. 26, 2014. Japans economy tumbled into its steepest contraction in more than five years after a 3 percentage point increase in the tax in April. Abe is weighing whether to go ahead with a hike to 10 percent next October, as legislated by the previous government. Photographer: Tomohiro Ohsumi/Bloomberg via Getty Images
Sakurajima volcano stands in Kagoshima, Japan, on Sunday, Oct. 26, 2014. Japans economy tumbled into its steepest contraction in more than five years after a 3 percentage point increase in the tax in April. Abe is weighing whether to go ahead with a hike to 10 percent next October, as legislated by the previous government. Photographer: Tomohiro Ohsumi/Bloomberg via Getty Images
MOUNT SAKURAJIMA VOLCANO, ERUPTION, JAPAN - AUGUST 22, 2013: The Mount Sakurajima Volcano, near Kagoshima Japan, is captured here spewing ash by a DigitalGlobe Satellite on August 22, 2013. (Photo DigitalGlobe via Getty Images)
MOUNT SAKURAJIMA VOLCANO, ERUPTION, JAPAN - AUGUST 22, 2013: The Mount Sakurajima Volcano, near Kagoshima Japan, is captured here spewing ash by a DigitalGlobe Satellite on August 22, 2013. (Photo DigitalGlobe via Getty Images)
MOUNT SAKURAJIMA, JAPAN - SEPTEMBER 29: (EDITORS NOTE: Image was created with a smartphone) The volcano on Mt Sakurajima erupts September 29, 2014 in the air over Mt Sakurajima, Japan. T (Photo by Chris McGrath/Getty Images)
KAGOSHIMA, JAPAN - AUGUST 18: (CHINA OUT, SOUTH KOREA OUT) In this aerial image, the volcanic smoke spews from Mount Sakurajima to cover the city center with ash on August 19, 2013 in Kagoshima, Japan. The Japan Meteorological Agency said Sakurajima volcano in southwestern Japan had a major eruption Sunday afternoon, spewing volcanic ash 5,000 meters into the sky. (Photo by The Asahi Shimbun via Getty Images)
KAGOSHIMA, JAPAN - AUGUST 18: (CHINA OUT, SOUTH KOREA OUT) Volcanic smoke spews from Mount Sakurajima on August 18, 2013 in Kagoshima, Japan. The Japan Meteorological Agency announced that Mount Sakurajima's volcanic ash was spewed to reach 5,000 meters into the sky. Massive amounts of ash covered Kagoshima City, prompting railway operators to temporarily stop train operations to remove ash from tracks. There were no reports of injuries.The volcano is located in the southern Japanese main island of Kyushu. (Photo by The Asahi Shimbun via Getty Images)
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