A full circle rainbow around the sun dazzled Rio Grande Valley residents last Friday. The rainbow was visible around 1 p.m., June 30, 2023.
San Antonio Express-News
Nora López
Several Rio Grande Valley residents were dazzled last Friday by what appeared to be a full-circle rainbow around the sun.
The effect, called a halo, was captured on camera by some Valley residents eager to document the phenomena.
One Reddit poster uploaded a photo of the cloudy sun circle rainbow.
Cloudy Sun Circle Rainbow
by u/Electrical_Shoe528 in RioGrandeValley
“The phenomenon is caused by ice crystals high in the atmosphere, which act like a prism to create both the halo, and the colors at the edges,” said Jon W. Zeitler, science and operations officer with the Austin-San Antonio NWS office.
Zeitler said we do occasionally see these halos in the San Antonio area, “especially when thunderstorms are occurring over the mountains in Mexico.”
“The thunderstorms lift moist air from near the ground, it condenses into drops and freezes in the upper part of the storms, and then strong upper level winds bring the ice crystals over our area. Many times, there are enough of the crystals that we only see high, overcast clouds. But if the amount of ice crystals is just right, the halos form instead, when the sun or moon are at the right angle (usually high in the sky).
He said these halos “are more common downwind of mountain ranges, places like the western states, and cities like Denver.”