If you looked up in the sky Thursday in the Chicago area, chances are you might have witnessed a seemingly unusual sight.
Viewers started reporting to NBC Chicago Thursday afternoon what they called an "alien ship cloud" or a "hole in the clouds."
"I opened my email and I'm flooded with these [pictures]," NBC 5 Storm Team Chief Meteorologist Brant Miller said.
According to Miller, it was actually what is known as a "hole punch cloud," sometimes referred to as a "fallstreak hole."
The National Weather Service reports such clouds are characterized as "a large circular or elliptical gap that can appear in cirrocumulus or altocumulus clouds."
Miller said a hole punch cloud is made up of an area clouds, super cool water droplets, or water that's liquid below freezing, and an ice crystal.
"What happens is that ice crystal attracts all those supercooled water droplets, turns them to ice crystals and then a precipitator falls out and that rainbow effect is those ice crystals acting as tiny prisms," Miller said.
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According to Miller, the ice crystals could have come from a passing airliner.
"That's what's happening in the sky when you see it. It's not some alien approaching us," Miller said.
The cloud formation isn't common since it requires several elements to line up, but it's also not incredibly rare, according to the Storm Team.
