The atmospheric phenomenon behind the mysterious glowing rings in the sky explained.
One of the most beautiful and mysterious phenomena in Earth’s atmosphere is the glowing ring that sometimes appears around the Sun or Moon. These bright circular formations, known as halos, have fascinated people for centuries and were once believed to predict storms, major weather changes or even supernatural events.
Today, scientists understand that halos are natural optical phenomena created when sunlight or moonlight interacts with tiny ice crystals suspended high in Earth’s atmosphere. Although they may look unusual or even surreal, halos are actually part of a fascinating family of atmospheric optics caused by the bending and reflection of light.
Depending on atmospheric conditions, halos can appear as complete glowing circles, colorful arcs or bright spots near the Sun.
How halos form in the atmosphere
Halos form when sunlight or moonlight passes through millions of tiny ice crystals located high in the atmosphere, usually inside cirrus or cirrostratus clouds. These clouds are extremely thin and often appear wispy or veil-like, sometimes covering large portions of the sky before weather systems arrive.
The ice crystals inside these clouds act like countless miniature prisms. As light enters and exits the crystals, it bends at specific angles and becomes redirected toward the observer. Under the right conditions, this process creates the bright circular ring visible around the Sun or Moon.
Most common halos are produced by hexagonal ice crystals that naturally refract light approximately 22 degrees away from the original light source. This is why the most familiar halo formation is called a “22-degree halo.” The geometry of the ice crystals is so precise that the phenomenon can appear almost perfectly symmetrical in the sky.
Although halos may seem rare, they occur far more often than many people realize. In many cases they are simply faint or partially hidden by thin cloud layers.
Why halos often appear before storms
For generations, sailors, farmers and weather observers noticed that halos frequently appeared before rain, snow or major weather changes. Interestingly, this traditional belief contains a great deal of scientific truth.
The thin cirrus and cirrostratus clouds responsible for halos are commonly associated with approaching low-pressure systems and warm fronts. These high clouds often arrive many hours before precipitation begins at the surface. As a result, the appearance of a halo can sometimes indicate that a storm system is moving closer.
This does not mean that every halo guarantees bad weather, but the phenomenon is often connected to changing atmospheric conditions. In some cases, rain or snow may develop within the following 24 to 48 hours after a prominent halo appears.
Because of this connection, halos became deeply embedded in weather folklore across many cultures around the world.
The difference between Sun halos and Moon halos
Halos can form around both the Sun and the Moon, although their appearance often differs significantly.
Sun halos are usually brighter and easier to notice because sunlight is extremely intense. In certain conditions, subtle rainbow-like colors may become visible along the inner edges of the ring, especially when the atmosphere is particularly clear.
Moon halos form through exactly the same process, but moonlight is far weaker than sunlight. Because of this, lunar halos generally appear pale white or slightly bluish instead of vividly colored. Even so, a large glowing ring surrounding the Moon on a cold winter night remains one of the most striking atmospheric displays visible to the naked eye.
Many people first notice moon halos during winter because cold-season atmospheric conditions often favor the formation of ice-crystal clouds high above the surface.
More than just a simple ring in the sky
Halos belong to a much larger family of atmospheric optical phenomena caused by ice crystals and the interaction of light with Earth’s atmosphere.
Under certain conditions, the same atmospheric processes can also produce:
- sun dogs,
- light pillars,
- tangent arcs,
- circumhorizontal arcs,
- and other rare luminous formations.
Some halo displays become incredibly complex, creating multiple glowing arcs and bright spots around the Sun simultaneously. These large atmospheric optical events can transform the sky into an extraordinary geometric display of light and color.
Scientists continue studying many of these phenomena because the exact shape, orientation and movement of ice crystals can create optical effects that are still not fully understood.
Why halos fascinate people around the world
Part of the fascination surrounding halos comes from their unusual appearance and the sense that they transform the ordinary sky into something almost otherworldly.
Ancient civilizations often interpreted halos as messages from the gods or signs of major events. In medieval Europe, moon halos were frequently associated with storms, harsh winters or supernatural beliefs. Similar stories and interpretations appeared in cultures across Asia, the Middle East and the Americas.
Even in the modern era, halos continue to attract enormous attention whenever dramatic photographs spread across social media. Their combination of atmospheric science and visual beauty makes them one of the most captivating natural phenomena visible from Earth.
Unlike many weather events, halos are calm, silent and almost dreamlike, appearing suddenly in the sky without thunder, wind or rain.
Are halos dangerous to observe?
The halo itself is completely harmless, but observing solar halos requires caution because looking directly at the Sun can seriously damage eyesight.
Meteorologists and astronomers recommend using buildings, trees or other objects to block the Sun while observing the surrounding halo safely. Sunglasses alone are not sufficient protection for prolonged direct viewing of the Sun.
Moon halos, however, are perfectly safe to observe directly because moonlight is far weaker and does not pose the same risks to human eyes.
One of the most beautiful phenomena in Earth’s atmosphere
Halos remain one of the most extraordinary examples of how Earth’s atmosphere can create breathtaking natural displays using nothing more than light, ice and geometry.
What appears at first glance to be a mysterious glowing ring is actually the result of incredibly precise atmospheric conditions occurring high above the planet. Tiny ice crystals floating in the upper atmosphere can transform ordinary sunlight and moonlight into spectacular circles and arcs visible across the sky.
Even today, seeing a giant halo surrounding the Sun or Moon continues to inspire curiosity, awe and fascination, reminding us how many beautiful and complex processes are constantly unfolding in the atmosphere above our heads.
