Photo: Matthew Cappucci/MyRadar.
Star-shaped hail seen in June 2026 near Arthur, Illinois.
Here’s a new one for extreme-weather buffs: star-shaped hail. Meteorologist and storm chaser Matthew Cappucci traveled miles to report on the rarity for the app My Radar. He shares his findings at the Washington Post.
“Anyone who knows me knows I have a thing for hail. An avid storm chaser, I’ve replaced 10 windshields. My dimpled, dented truck looks like a golf ball. I keep a freezer in the back seat.
“But the hail I encountered earlier this month in Arthur, Illinois, was unlike any other stones I’ve seen. They were as wide as baseballs — but shaped like stars.
“The National Weather Service had issued a severe thunderstorm warning for Douglas and Moultrie counties at 6:16 p.m. on June 17. The nearby town of Decatur, about 30 miles to the west, had just logged a 78 mph wind gust. As I approached Arthur from the south, I knew I was getting into a gnarly storm.
“Before the rain even began, the sky turned a neon green-blue. It evolved into a phosphorescent aquamarine. Contrary to popular belief, the infamous ‘green sky’ phenomenon doesn’t signify an impending tornado — but it’s nearly a guarantee of hail.
“That’s because severe thunderstorms usually happen in the late afternoon near peak heating, which comes two or three hours before sunset. At that time of day, the sun — lower in the sky — has to shine through our atmosphere at an angle, meaning the light passes through more of it. Much of the blue light (shorter wavelengths) is scattered away; the longer wavelengths, like yellow and red, are better at penetrating deeper into the atmosphere and reaching the ground.
“Tall thunderstorms, however, scatter blue and bluish-green light. That’s especially true if the clouds are carrying lots of hail. Added together, the yellow and blue make green.
“As I drove north on Route 1500E, the rain arrived suddenly, along with winds strong enough to rock my truck back and forth. I was sneaking in behind the worst of the storm; my goal was to arrive in Arthur immediately after the hail. I wanted to collect some without losing my windshield.
“But even five miles south of the storm’s core, I still experienced about 30 seconds of hail. Apparently the storm’s spinning updraft was enough to fling random tennis ball-sized stones out the side. … Only three or four hit my truck.
“Arriving in Arthur, however, the landscape was littered with stones between 1.5 and 3 inches in diameter. Most were about two inches across. They weren’t round, however — they were shaped like stars. Each had little arms or antennas. If they hadn’t been so damaging, they’d almost be cute.
“What caused the wonky protuberances? Wet growth.
“Hail forms high aloft in storm clouds, where temperatures are between minus-22 and 14 degrees Fahrenheit. Too much colder, and the air is too dry to hold moisture. Any warmer, and hailstones take too long to freeze.
“There are two different types of hailstone growth. Each are responsible for forming different types of layers. …
“Dry growth tends to support rounder hailstones. Wet growth, however, happens at warmer temperatures. Larger droplets take longer to freeze. That gradual freezing keeps the edges of the hailstone ‘sticky’ in a sense, as if the growing stone were coated in glue. Smaller hail embryos, akin to the seeds of undeveloped hailstones, collide with the sticky stones. They fuse together, forming weird protrusions. The jagged spikes get coated in new layers of ice, and the hailstone grows in curious ways.
“Atmospheric scientists are still working to learn more about hail. What role does the shape of hailstones have on the force it imparts when it hits the ground? Do hailstones have varying levels of hardness? And what factors dictate the size distribution of hail?”
More at the Post, here.
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