A Rainbow Can Occur at Night

    Most people grow up believing that rainbows belong only to the daytime appearing after rain when bright sunlight passes through droplets in the sky. Yet nature has a quiet secret that many never witness: a rainbow can also appear at night. This rare and enchanting phenomenon is known as a moonbow or lunar rainbow. Instead of sunlight, a moonbow is created by the soft, reflected glow of the Moon. Because the Moon does not produce its own light, but merely reflects the Sun’s rays, the resulting nighttime rainbow is much fainter, more delicate, and often invisible unless conditions are perfect.

How a Moonbow Forms

    Although a moonbow looks mysterious, the science behind it is identical to that of a daytime rainbow. Moonlight enters tiny droplets of rain or mist, bends, reflects inside the droplet, then bends again as it exits splitting into multiple colors. The difference lies in brightness. Moonlight is hundreds of thousands of times weaker than sunlight, which makes the colors of a moonbow extremely soft. To the human eye, a moonbow often appears white or silver, but when captured using a long-exposure camera, the full spectrum of colors becomes visible. This happens because our eyes rely on rod cells in low-light conditions, and these cells cannot detect color. Cameras, however, can gather light over several seconds, revealing the rainbow’s hidden hues.

The Rare Conditions Required

    A moonbow is far more difficult to see than a normal rainbow because it requires a very specific combination of natural elements. The Moon must be full or nearly full so that it produces enough brightness to illuminate the night sky. It must also be low on the horizon so that the angle of moonlight can refract properly through the droplets. There must be water in the air—rainfall, waterfall mist, ocean spray, or fog directly opposite the Moon. The sky needs to be extremely dark, with little to no artificial light nearby, because even a small amount of brightness can overwhelm the delicate moonbow. All these factors must happen at the same time, which is why moonbows are considered one of the rarest sky phenomena.

Where Moonbows Appear Most Often

    While moonbows can theoretically appear anywhere, they are most commonly found in locations with heavy mist and low light pollution. Certain places in the world have gained fame for frequent moonbow sightings, including the massive Victoria Falls on the border of Zambia and Zimbabwe, where continuous waterfall spray meets the African night sky. In the United States, moonbows are regularly seen at Yosemite National Park during the spring runoff and at Cumberland Falls in Kentucky, where local conditions consistently create strong mist under a bright moon. In Hawaii, the unique climate of Waimea Canyon also produces moonbows that arc beautifully over the landscape. These locations show that moonbows prefer wild, natural environments far from bright city lights.

Why Moonbows Captivate Both Science and Art

    Moonbows are not only visually stunning—they are also scientifically fascinating. Atmospheric scientists study them to understand how refraction, light scattering, and moisture behave under low-light conditions. Moonbows provide insight into how the human eye perceives color at night and how different wavelengths of light separate under the dim glow of lunar illumination. Photographers are equally enchanted by moonbows. Capturing one requires patience, timing, and technical skill. Long-exposure photography reveals the rainbow’s full colors, turning an almost invisible arc into a breathtaking display. Many photographers travel worldwide for the chance to capture a moonbow, often waiting hours in darkness for the Moon to rise high enough, the clouds to clear, and the mist to thicken just right.

Moonbows in Culture and Myth

    Throughout history, moonbows have inspired myths, legends, and spiritual stories. In many cultures, they were seen as symbols of protection, transformation, or messages from the night sky. Their rarity made them feel supernatural, as if the moon had painted a secret rainbow that only a few could ever see. Even today, when science has explained their formation, moonbows retain their dreamlike quality. Witnessing one feels like encountering a miracle of silence and light—an event that reminds us of the hidden wonders of the natural world.

The Quiet Magic of a Nighttime Rainbow

    A moonbow is a reminder that the night is full of beauty often overlooked. While daytime rainbows burst with color and brightness, moonbows whisper their presence softly, appearing faintly across dark skies and disappearing before most people even notice. This delicate phenomenon proves that nature continues to create masterpieces even after the sun has set. For those lucky enough to witness one, a moonbow becomes a moment of pure wonder—a quiet, magical arc painted by the Moon itself.

Sources:

• NASA – Atmospheric and optical light phenomena

• National Geographic – Features on lunar rainbows and low-light atmospheric events

• Royal Meteorological Society – Scientific explanation of moonbows

• Smithsonian Magazine – Articles on rare nighttime optical phenomena

• U.S. National Park Service – Documentation of moonbow occurrences in Yosemite and Cumberland Falls