ST. LOUIS — Numerous 5 On Your Side viewers saw numerous rainbows drifting through the skies of the St. Louis region on Thursday, just days before the city's LGBTQIA+ Pride celebration was scheduled to start.
"Just saw the color spectrum in a cloud. Never witnessed that in 60+ years!" 5 On Your Side Weather Watcher Karl Peifer said.
The cloud rainbows are caused by a relatively rare weather phenomena, according to the National Oceanic Atmospheric Administration (NOAA). Unlike regular rainbows, which are caused by sunlight passing through raindrops falling in the sky, rainbow clouds require much more specific conditions described as cloud iridescence.
" It usually happens in altocumulus, cirrocumulus, lenticular and cirrus clouds. Iridescent clouds happen because of diffraction – a phenomenon that occurs when small water droplets or small ice crystals scatter the sun's light," NOAA said.
Cloud iridescence is rare because the cloud must be thin enough to allow light to pass through and have water droplets or ice crystals that are relatively the same size.
"When that happens, the sun's rays encounter just a few droplets at at time," NOAA said. "For this reason, semi-transparent clouds or clouds that are just forming are the ones most likely to have iridescence."
The clouds were just a taste of the amount of rainbows St. Louis is expected to see Saturday and Sunday when PrideSTL kicks off its annual Pride Fest celebration. The event will culminate at noon on Sunday with the Grand Pride Parade, which 5 On Your Side will be participating in.
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