A rare atmospheric phenomenon known as a circumhorizontal arc was captured in a photograph near North Fork Mountain.
Key facts
- •The featured photograph was taken in 2021 near North Fork Mountain, West Virginia.
- •Circumhorizontal arcs appear parallel to the horizon and are considered somewhat unusual to observe.
- •The effect is caused by ice crystals in cirrus clouds acting as floating prisms.
- •The sun must be at least 58 degrees high for the arc to form.
- •The specific cloud type identified in the image is cirrus fibratus.
NASA's Astronomy Picture of the Day for August 2, 2026, features a photograph of a circumhorizontal arc, informally called a fire rainbow, taken near North Fork Mountain in West Virginia. The image captures the colorful optical effect occurring within a cirrus fibratus cloud.
Conditions for a Fire Rainbow
A circumhorizontal arc occurs when sunlight is refracted by flat, hexagonal ice crystals within high-altitude cirrus clouds. For the phenomenon to be visible, the sun must be positioned at least 58 degrees high in the sky, and the ice crystals must be aligned horizontally to act as prisms.
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This article was independently rewritten by ManyPress editorial AI from reporting originally published by NASA Breaking News.
