It looks like a UFO or some strange portal to another world, but it's actually an unusual phenomenon known as a fallstreak hole. 

What You Need To Know

  • Fallstreak holes can be confused for UFOs 

  • They form through a process of ice crystal nucleation

  • They're often created by passing aircraft

A few weeks ago, several folks up in northern Wisconsin reported seeing a very strange sight in the mid-afternoon sky. Some said it looked like a UFO, while others thought it might be a portal to another galaxy. 

Michele Nevue captured these pictures in Chetek, Wisconsin. 

Kimberly Schwark captured this amazing picture in Rice Lake, Wisconsin. 

It's easy to see why this could be confused for something much more sinister. 

This is actually a meteorological phenomenon known as a fallstreak hole or a hole punch cloud, and they are completely harmless. 

A fallstreak hole is a large circular or elliptical gap that can appear in cirrocumulus or altocumulus clouds.

How do they form?

High to mid-level clouds, such as altocumulus, are often composed of tiny water droplets that are much colder than freezing, but are still liquid.

These "supercooled" water droplets need a "reason" to freeze, which usually comes in the form of ice crystals. Planes passing through the cloud layer can bring these ice crystals.

Once the ice crystals are introduced, the water droplets quickly freeze, grow and start to fall. A hole is left behind, which expands outward as neighboring droplets also freeze.

Next time you see this rare sight, make sure to snap some photos and enjoy!