Cutting Open a Hailstone: Reading the Storm's Biography in Ice

The Updraft Elevator

The layering happens because hailstones don't fall straight down. A developing thunderstorm's updraft—the column of rising air that powers the entire system—can reach speeds of 100 miles per hour in severe supercells. According to NOAA's National Severe Storms Laboratory, these updrafts suspend hailstones in the cloud, sometimes for approximately 15 to 30 minutes, cycling them through different temperature and moisture zones like a deranged amusement park ride.

Here's what most people get wrong: they imagine hailstones forming at the top of the cloud and simply falling. In reality, a stone might start as a tiny ice pellet or frozen raindrop, get lofted upward, accumulate a layer of ice, fall partway down as it grows too heavy for the updraft at that altitude, then get caught in another surge of rising air and lifted again. Each trip through the updraft adds another layer. A hailstone with twelve layers typically made six complete round trips—up, down, up, down—before finally growing heavy enough to overwhelm the updraft entirely and plummet to the ground.

The thickness of each layer varies based on how much supercooled water the stone encountered during that particular cycle and how long it spent in that zone. A thick clear layer suggests the stone spent extended time in a moisture-rich region where wet growth could proceed. A thin opaque layer might indicate a brief pass through a dry, cold zone. Some hailstones show layers of different thicknesses on opposite sides, evidence that the stone tumbled or rotated as it grew, exposing different surfaces to different conditions.

Reading the Final Chapter

The outermost layer is almost always opaque, and for good reason. When a hailstone finally exits the updraft—either because it grew too massive or because the storm's dynamics shifted—it passes through the coldest air at the cloud top or gets ejected into the dry air surrounding the storm. This final exposure creates rapid freezing conditions that trap the maximum concentration of air bubbles. That milky outer shell is the stone's last moment in the storm, frozen in place.

According to NOAA's National Severe Storms Laboratory, researchers occasionally find hailstones with unusual layering patterns that reveal specific storm behaviors. Stones with extremely thick clear layers suggest they spent time in the storm's main updraft where liquid water content is highest. Stones with many thin layers indicate rapid cycling through a pulsing updraft. Some large hailstones show evidence of partial melting between layers—thin zones where the ice appears to have refrozen after liquid water penetrated the outer surface—suggesting the stone briefly dropped into above-freezing air before being lofted back up.

The largest hailstones on record, including the 8-inch diameter stone that fell in Vivian, South Dakota in 2010, show extraordinarily complex internal structures when analyzed. These giants typically display approximately 15 to 20 or more distinct layers, indicating they remained aloft for extended periods in exceptionally powerful updrafts. The sheer number of cycles required to build such mass—accumulating ice roughly a millimeter at a time during each pass—means these stones spent upward of approximately 20 to 30 minutes being constructed by the storm.

Cross-sections also reveal that not all hailstones are spherical all the way through. Many show an irregular or elongated core—perhaps a frozen raindrop or small ice crystal—that served as the initial embryo. The subsequent layers wrap around this nucleus, gradually building toward a more spherical shape as the stone tumbles and rotates during its journey. Stones that didn't rotate much sometimes retain oblong or lobed shapes, with layering that's thicker on one side than the other.

Scientists studying hailstone cross-sections can sometimes reconstruct the storm's structure and intensity from the ice itself. The ratio of clear to opaque layers provides clues about the temperature profile inside the cloud. The overall size and layer count suggest updraft strength and duration. In a sense, each hailstone is a data logger that recorded conditions inside a storm system that may have dissipated hours before the stone was found and sectioned.

If you find a large hailstone, the standard procedure for preservation is immediate freezing—placing it in a freezer within minutes prevents the layers from melting into each other and erasing the record. Then you can section it with a sharp blade (a clean cut through the center works best) and photograph the cross-section against a dark background with strong side lighting, which makes the alternating layers dramatically visible. What you're seeing is a timeline compressed into ice: every layer a chapter, every circuit through the storm a paragraph in a biography written in freezing water and trapped air.