A ring of light circled the Sun over Baltimore Sunday morning, and it had nothing to do with rain. The striking display, known as a sun halo, prompted WBAL-TV meteorologist Alena Lee to set the record straight for viewers with a simple message: this is not a rainbow.
Lee showed the sun halo appearing over Baltimore on Sunday morning, according to WBAL-TV. The station's report made clear the distinction was intentional, framing the piece around the idea that the glowing ring in the sky, however rainbow-like it might look at a glance, is actually a completely different atmospheric phenomenon with its own name and its own cause.
What Exactly Is a Sun Halo?
A sun halo is a ring of pale light around the Sun caused by sunlight refracting through ice crystals suspended in high cirrus or cirrostratus clouds, per the Farmers' Almanac. Those clouds typically drift 20,000 feet or more above the ground, far higher than the rain clouds most people associate with wet weather, and are made up of millions of tiny ice crystals that bend sunlight as it enters and exits them, according to EarthSky.
The resulting ring is commonly called a 22-degree halo because its radius consistently measures around 22 degrees, EarthSky notes. Solar halos can even show subtle color, with red appearing on the inner edge and blue toward the outside, a detail EarthSky says tends to be more noticeable in halos around the Sun than those around the Moon.
Why It Looks Like a Rainbow but Isn't
The confusion between sun halos and rainbows is understandable, but the two form in completely different ways. Rainbows are made by water droplets in low rain showers, while sun halos are made by ice crystals in high cirrus clouds, the Farmers' Almanac explains. Rainbows also appear opposite the Sun in the sky, while halos encircle the Sun itself, a distinction that lines up with why Lee was careful to clarify what Baltimore viewers were seeing.
The National Weather Service notes that the atmosphere is capable of producing a range of colorful optical effects when conditions align, including halos, sun pillars and sundogs. NOAA's JetStream program similarly describes cirrostratus cloud veils as being distinguished by the halo phenomenon nearly always produced when the Sun or Moon shines through that cloud layer.
Could It Signal Changing Weather?
Beyond their visual appeal, sun halos carry a loose reputation as weather indicators. Cirrostratus clouds usually come 12 to 24 hours before a rain or snowstorm, according to UCAR SciEd, since the thin, high clouds that produce halos often arrive ahead of an approaching warm front. The Farmers' Almanac frames this the same way, describing it as a general pattern rather than a guaranteed forecast for any specific location.
Halos themselves are far from rare on a global scale. They can occur anywhere on the planet during winter or summer, EarthSky notes, since all it takes is sunlight passing through the right kind of high, ice-crystal-laden cloud. For Baltimore residents who caught Sunday's display, it offered a brief, glowing reminder of how much is happening in the sky far above the clouds most people notice day to day.
