Halo
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Sun halo is one of those "stop-and-stare" moments—a giant, glowing ring circling the sun that looks like something out of a sci-fi movie. Despite how otherworldly they look, the explanation is actually grounded in simple atmospheric physics.
What causes a Sun Halo?
The most common version is the 22° halo. It isn't caused by rain (like a rainbow), but by ice crystals high up in the atmosphere.
The Clouds: These halos usually form through cirrus or cirrostratus clouds. These are thin, wispy clouds located 20,000 feet or higher where the air is always freezing.
The Crystals: These clouds are made of millions of tiny, hexagonal (six-sided) ice crystals.
Refraction: As sunlight enters one side of the ice crystal and exits the other, it bends at a specific angle—exactly 22 degrees. This consistency creates a perfect circle of light around the sun.
Key Features to Look For
The "Inner Dark": You'll notice the sky inside the ring often looks darker than the sky outside of it.
Faint Colors: While they look white at first glance, the inner edge is often tinted slightly red, while the outer edge can have a faint blue or violet hue.
Predicting Weather: Folklore says a halo is a sign of approaching rain or snow. There's actually some truth to this! Cirrus clouds often precede a warm front, which brings precipitation within 24 to 48 hours.
Safety First
It's easy to get mesmerized, but don't look directly at the sun while trying to spot a halo.
Pro-tip: Use your hand or a building to block the sun itself so you can see the ring clearly without damaging your eyes.
Fun Fact: If you see "bright spots" on the left and right sides of the halo, those are called Sun Dogs(parhelia). They are caused by the same ice crystals, just oriented horizontally as they sink through the air.
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