If you’ve ever looked up on a cold, clear day and seen a perfect ring of light encircling the sun, you’ve witnessed one of the atmosphere’s most beautiful optical tricks: a 22-degree solar halo. Mountaineers, skiers, and climbers often encounter this phenomenon high in the mountains—where ice crystals in the air act like countless tiny prisms, bending sunlight into a glowing circle around our nearest star. It’s not magic, but it sure feels like it.
A 22-degree halo forms when sunlight passes through millions of hexagonal ice crystals suspended in cirrostratus clouds, which often sit high in the troposphere. The light refracts—or bends—at an angle of 22 degrees, producing a ring that’s sometimes white, sometimes faintly rainbow-hued. It’s one of the more common halos, though it never loses its power to stop climbers mid-ascent for a quick photo and a moment of awe.
Sometimes people refer to these as “sun dogs.” All sun dogs are solar halos, but not all solar halos are sun dogs. Sun dogs are a specific kind of solar halo. The light refraction on these is brightest parallel to the sun, making it look like there are suns on either side of the sun.
In Greek Mythology, it was believed that the bright lights on either side of the sun were the dogs of Zeus. In other words, these were “sun dogs.” Similarly, the Inuit in the Arctic believed that these were spirits in the sky on either side of the sun.
Regardless of the mythology, these kinds of halos often do come with a message. Cirrostratus clouds often precede warm fronts and hint at incoming weather, usually rain or snow. Indeed, the weather is often going to arrive within six to twelve hours of the phenomenon.
Though it might mean you’re about to get wet, there’s still something poetic about seeing a solar halo while perched high on a ridge—sunlight, ice, and atmosphere aligning just right to remind you that you’re part of something vast and dynamic. It’s a wink from nature, a reminder that beauty and science often share the same space, especially when viewed from the mountains…