Halo around the sun: What's causing this solar phenomenon across the Riverbend?

ALTON – Riverbend reader Lindsey Krankel sent a photo of quite the atmospheric phenomenon – a halo around the sun known as a "sun dog."

National Weather Service (NWS) Meteorologist Patrick Walsh said the halo around the sun is not due to the current temperature, which is struggling to reach even 10 degrees as Wednesday's high is predicted to only be seven, but instead has to do with clouds and otherwise clear days. The phenomenon of a halo being seen surrounding the sun in a perfect circle is actually much more similar to a rainbow.

Wispy clouds high in the sky, often looking like singular strokes of a paintbrush covered in white, are called cirrus clouds. They are made of ice crystals and reside high in the upper reaches of the atmosphere – much higher than the low, gray stratus clouds and even the puffy, white cumulus sorts.

In order to make a halo around the sun as the one seen across the Riverbend today, such a cirrus cloud would have to move in front of the sun and be exceptionally thin. The sun's light then refracts from the ice crystals composing the cloud, which creates the illusion of a halo around the sun.

When asked if they exclusively occur in cold climates, Walsh said he has seen them in Mexico and can pretty much happen anywhere with a clear day and a skinny cirrus cloud.

"If you haven't stepped outside today, you should brave the cold to see this amazing ice crystal phenomenon!" Krankel said in her email submission.

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