Have you ever gazed up at the sky and witnessed what appears to be a flaming rainbow stretching across the horizon? You might think you’re experiencing a supernatural phenomenon or even a dangerous natural disaster. The truth is far more fascinating than fiction.
These mesmerizing displays, popularly called “fire rainbows,” are neither fires nor rainbows. They’re actually one of nature’s most extraordinary optical illusions, created by the perfect alignment of ice crystals, sunlight, and atmospheric conditions. When these cosmic elements converge, they produce a spectacle so breathtaking that ancient cultures often considered them divine messages.
The Misleading Name That Captured Imaginations
The term “fire rainbow” is misleading since it’s neither a rainbow nor related to fire, though its exact origin is unclear. The name may originate in the occasional flame-like appearance when it occurs in fragmentary cirrus clouds that resemble bright flames lighting up the sky.
The scientific name is circumhorizontal arc, an optical phenomenon belonging to the family of ice halos formed by sunlight refraction in plate-shaped ice crystals suspended in the atmosphere. When people spot these formations, they can’t take photos fast enough, and many images go viral on the internet because the phenomenon is so rare.
The Scientific Marvel Behind the Spectacle
Fire rainbows form when sunlight enters horizontally-oriented, flat, hexagonal ice crystals through a vertical side face and leaves through the near horizontal bottom face. The 90-degree inclination between ray entrance and exit faces produces well-separated spectral colors, and this bending of light is equivalent to light passing through a prism, with the whole cirrus cloud section behaving like a massive prism.
When sunlight enters the ice crystals, it refracts or bends and exits at a precise angle, causing different colors to separate and producing the striking array of colors seen in fire rainbows. The effect is like sending a beam of light through millions of prisms, with sunlight passing through the vertical face of ice crystals then being refracted downward through the crystal’s bottom face toward the ground, splitting into separate bands of colored light.
Perfect Conditions Create Impossible Beauty
Fire rainbows require the sun to be at least 58 degrees above the horizon. Ice crystals must be hexagonal in shape with their faces running parallel to the ground. Thin, wispy cirrus clouds containing plate-shaped ice crystals are essential, and they’re more commonly seen in mid-latitudes during summer when the sun’s angle is optimal.
These phenomena occur in cirrus clouds found at altitudes of 20,000 feet or higher, where temperatures are extremely cold. Clear skies enhance visibility, making it easier to spot the vibrant arc during midday when the sun is at its peak altitude.
Geographic Lottery of Visibility
The solar variety is impossible to see at locations north of 55°N or south of 55°S, though it’s relatively common in the United States, seen several times each summer in any one place, while being rare in northern Europe. In London, the sun is only high enough for a mere 140 hours between May to July, while Los Angeles enjoys 670 hours between March to September.
European weather is often cloudy, and fire rainbows would likely be masked by low- and middle-level clouds, making them more than 10-20 times more likely to be seen in the United States. If you’re positioned north of 55° N or south of 55° S, your chances of seeing a fire rainbow are almost nonexistent.
Distinguishing Real From Fake Phenomena
Circumhorizontal arcs are sometimes confused with cloud iridescence, which causes clouds to appear multi-colored through diffraction rather than refraction. Fire rainbows always have a fixed location below the sun at 46 degrees, with color bands running horizontally with red on top, producing pure spectral colors more vivid than regular rainbows, while cloud iridescence appears in different positions with random color sequences and a washed-out appearance.
Recent AI-generated images circulating on social media are often fake, as real circumhorizontal arcs are always horizontal with colors parallel to each other and the same color pattern as rainbows – red at the top and purple at the bottom. Some people posting pictures of what they think are fire rainbows are actually observing another phenomenon called sun dogs, which form to the right and left of a rising or setting sun.
The Emotional Impact of Witnessing the Phenomenon
Tracey Smith, who captured a viral fire rainbow photo over South Carolina, said it reminded her of a deceased friend and wrote “I’m sure she came to visit us on the beach we all love!” The South Carolina sighting in 2015 was dubbed a “multi-colored angel” and went viral.
Fire rainbows captivate viewers with their surreal, flame-like appearance, and seeing one feels almost magical due to their rarity and fleeting nature, with colors appearing brighter and more intense than traditional rainbows. One photographer described their first experience seeing one as lasting about 10 minutes with brightness and clarity visible to people hundreds of miles away.
Duration and Frequency of Appearances
Fire rainbows have considerable angular extent and rarely appear complete, with only fragments visible when the halo-forming cloud is small or patchy. When they do appear, they can span hundreds of miles and last for hours. One famous occurrence hung for about an hour across a several-hundred-square-mile area of sky above northern Idaho on June 3, 2006.
The frequency depends entirely on the location and latitude of the observer, being relatively common throughout the United States but rare in northern Europe, requiring ice crystal-containing clouds in the right position and light sources at 58 degrees or higher elevation. Fire rainbows can also occur at night with moonlight under the same conditions, requiring a high moon and parallel ice crystals, though lunar versions are easily spotted despite being truly rare.
Photography and Documentation Challenges
If you’re lucky enough to spot a fire rainbow, use a high-quality camera to photograph the vibrant arc and adjust settings to emphasize vivid colors with proper exposure. Look for them whenever you see cirrus clouds with the sun or moon high in the sky, and wearing polarizing sunglasses aids visibility, especially when the arc is dim.
iPhone Photography School recommends using HDR mode on smartphone cameras to capture details and highlights in both clouds and ground without over-exposing either. Professional photographers consider capturing fire rainbows a rare opportunity, with images representing what some would call extraordinary atmospheric phenomena.
Understanding the Deadly Beauty
Despite their name suggesting danger, fire rainbows pose no threat to observers. The “deadly” aspect refers to their breathtaking beauty that can leave viewers stunned and emotionally moved. These are among the rarest of all naturally occurring atmospheric phenomena, requiring cirrus clouds at least 20,000 feet in the air with precisely the right amount of ice crystals and the sun hitting clouds at exactly 58 degrees.
The conditions must be extremely precise, requiring the sun at 58 degrees elevation or greater, high altitude cirrus or cirrostratus clouds with ice crystals, and sunlight entering crystals at a specific angle to refract light, which is why circumhorizontal arcs are such rare phenomena to see. Their beauty lies not in any destructive power, but in nature’s ability to create something so spectacular that witnesses often describe the experience as life-changing.
Fire rainbows remind us that our atmosphere holds secrets capable of producing moments of pure wonder. These fleeting displays of celestial artistry prove that sometimes the most beautiful phenomena require the most precise conditions to exist. The next time you see wispy cirrus clouds on a clear summer day with the sun high overhead, look carefully – you might witness one of nature’s most extraordinary magic tricks painting the sky in impossible colors.
What do you think about it? Have you ever been fortunate enough to witness this rare atmospheric spectacle yourself?
