Strange Clouds Appear in the Sky — But Scientists Have a Fascinating Explanation

A strange formation in the sky can instantly make people stop, take out their phones and wonder what they’re witnessing.

That’s exactly why images showing enormous circular openings in otherwise continuous cloud layers frequently attract attention online. With sunlight pouring through the center, the formations can resemble giant portals, enormous eyes or even openings created by something passing through the atmosphere.

Despite their mysterious appearance, however, there is a scientific explanation.

The phenomenon is commonly known as a fallstreak hole, or more dramatically, a hole-punch cloud.

It Can Look Like Someone Cut a Hole Through the Clouds

Fallstreak holes are particularly striking because of their unusual shape.

Instead of clouds gradually fading away, observers may see a relatively well-defined circular or oval opening surrounded by an otherwise continuous cloud layer.

Sometimes thin, wispy trails of ice crystals appear underneath the opening. When sunlight passes through at the right angle, the entire formation can become even more dramatic.

It’s easy to understand why photographs of them generate unusual theories online.

But the real explanation involves an interesting combination of water, temperature and ice.

Water Can Remain Liquid Below Freezing

The clouds associated with fallstreak holes can contain what meteorologists call supercooled water droplets.

These are tiny droplets that remain liquid even though the surrounding temperature is below water’s normal freezing point.

They can remain in this unstable condition until something triggers them to freeze.

Once some of those droplets begin turning into ice crystals, an atmospheric chain reaction can follow.

The newly formed ice crystals grow while nearby liquid droplets evaporate, gradually producing an opening in the cloud layer.

From the ground, that opening can appear surprisingly large and symmetrical.

Airplanes Can Sometimes Trigger the Process

One of the most fascinating parts of the phenomenon is that aircraft can sometimes provide the disturbance necessary to begin it.

When an airplane travels through a cloud containing supercooled droplets, changes in pressure and temperature around its wings—or around propellers on certain aircraft—can encourage some droplets to freeze.

Once ice crystals begin forming, the process can spread through the surrounding area.

The result may become visible as a hole that expands through the cloud layer.

So while an aircraft can sometimes help trigger a fallstreak hole, the dramatic formation itself results from natural atmospheric processes involving supercooled water and ice.

Why Do They Become So Large?

The transformation doesn’t necessarily stop where it begins.

As ice crystals develop and fall from the cloud, additional droplets can evaporate around them. This allows the clear area to expand.

Depending on atmospheric conditions, observers may eventually see a massive circular or elongated opening stretching across the sky.

The falling ice crystals can also create wispy formations beneath the hole, adding to its unusual appearance.

From the ground, the combination can look almost unreal.

Social Media Makes Them Seem Even More Mysterious

Before unusual weather photographs could spread instantly around the world, many people might have gone their entire lives without seeing a fallstreak hole.

Today, one dramatic photograph can reach millions of people within hours.

Without context, viewers may suggest everything from UFOs to secret experiments or unexplained atmospheric disturbances.

There’s nothing wrong with being fascinated by an unusual sky.

But identifying the cloud type before jumping to extraordinary conclusions usually reveals something even more interesting: Earth’s atmosphere is capable of producing spectacular formations entirely on its own.

Not Every Circular Cloud Is a Fallstreak Hole

Photographs alone should still be interpreted carefully.

Clouds can take many unusual forms, and perspective, lighting and image editing can dramatically change how a formation appears.

A circular opening isn’t automatically proof that a particular photograph shows a fallstreak hole.

Meteorologists can make a more confident identification by considering the cloud type, weather conditions, location and timing.

Nature Doesn’t Need Special Effects

Perhaps that’s what makes fallstreak holes so fascinating.

There doesn’t need to be a mysterious object hiding above the clouds or an unexplained force creating the opening.

Under the right conditions, tiny droplets of supercooled water begin freezing, ice crystals develop, surrounding droplets disappear—and an enormous opening can emerge in the sky.

For anyone lucky enough to witness one, the result can look like something from a science-fiction movie.

But sometimes the strangest things above us have an explanation that’s just as fascinating as the mystery.