PHOENIX — Ever seen a rainbow in the dark? You can, when weather conditions are just right.
It's called a moon halo, lunar halo or a "moon dog." Usually, you'll see more of these rings around the moon when the weather is getting cooler. The optical illusion is the result of light refraction of moonlight off of ice crystals in the upper atmosphere.
In effect, these suspended or falling flecks of ice mean the atmosphere is transformed into a giant lens causing arcs and halos to appear around the moon at night. This lens is about 20,000 feet above us.
These ice crystals also demonstrate a prism effect that separates white light from the sun or is reflected by the moon into various individual colors just like the atmospheric effect that creates a rainbow.
The effect is so striking that it has given rise to a wealth of folklore and superstition. The most common is when you see a ring around the moon, rain will come soon.
Do you have questions about the weather? Email kpnx-connect@12news.com or text us at (602) 444-1212.
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