Hail typically conjures images of small, pea-sized ice pellets bouncing harmlessly off a sidewalk, but the largest hailstones produced by the most powerful thunderstorms can grow to the size of softballs or larger, falling with enough force to shatter windshields, dent car roofs and punch holes through siding and shingles. These giant hailstones form inside some of the most intense thunderstorms on the planet, and understanding how a piece of ice can grow so large before falling has become an important part of forecasting where the most damaging storms are likely to strike.
How a Hailstone Grows Layer by Layer Inside a Storm
Hail begins as a small ice pellet high inside a thunderstorm, where strong updrafts, columns of rapidly rising air, keep the developing stone suspended in a region of the cloud cold enough to freeze supercooled water droplets onto its surface. Each time the growing stone is caught in a fresh updraft and carried back up into that cold layer, it picks up another layer of ice, growing larger with every cycle, similar in principle to the layers of an onion. The size a hailstone ultimately reaches depends heavily on how strong the storm’s updraft is and how many times the stone manages to be recirculated before finally becoming too heavy for the updraft to support any longer. The most powerful thunderstorms, capable of sustaining updrafts strong enough to suspend a stone the size of a golf ball or larger, are the ones that produce the rare giant hail capable of causing serious damage on the ground.
What It Takes to Produce Softball-Sized Hail
Softball-sized hail, generally defined as stones around four inches in diameter, requires an updraft strong enough to hold a piece of ice that heavy aloft for an extended period, a threshold only the most intense supercell thunderstorms typically reach. These storms are characterized by a persistent, rotating updraft that can sustain wind speeds well over 100 miles per hour vertically, strong enough to keep a stone the size of a baseball or softball suspended in the storm’s coldest layers long enough to keep accumulating ice. Because that combination of atmospheric ingredients is relatively rare, giant hail events tend to be concentrated in specific storm systems rather than spread evenly across every thunderstorm, which is why forecasters treat confirmed reports of very large hail as an indicator that a storm has reached an unusually intense and dangerous stage.
The Physics Behind Hail’s Destructive Impact
The damage caused by large hail comes down to a combination of mass and terminal velocity, the speed at which a falling object stops accelerating because air resistance balances gravity. A stone the size of a softball can weigh several ounces and fall at speeds exceeding 100 miles per hour by the time it reaches the ground, delivering an impact force capable of cracking a windshield, punching through a roof or causing serious injury to anyone caught outside without shelter. That combination of size and speed is why giant hail causes damage on a different scale than the small, pea-sized hail most people are familiar with, which typically causes little more than surface cosmetic damage even after a lengthy storm.
Where Giant Hail Is Most Likely to Fall
Giant hail is not evenly distributed across the country; it clusters in regions where the atmospheric conditions needed to sustain powerful supercell thunderstorms occur most often. A broad corridor stretching across the central and southern Great Plains, sometimes referred to informally as hail alley, sees some of the most frequent large hail events in the world, driven by the collision of warm, moist air from the Gulf of Mexico with drier air masses moving in from the west. Storms in this region regularly produce hail large enough to total vehicles and destroy roofing across entire neighborhoods, and insurance industry data has repeatedly identified hail, rather than tornadoes or straight-line wind, as one of the costliest recurring sources of severe weather damage in the affected states.
Staying Safe When Giant Hail Threatens
Because large hail falls with so much force, the safest response when a severe thunderstorm warning mentions giant hail is to get indoors and away from windows immediately rather than trying to move a vehicle to shelter once the storm has already arrived. The National Weather Service advises staying under sturdy shelter, avoiding skylights and large windows, and treating any warning that specifically calls for very large hail as a signal that the storm producing it is operating at an unusually intense level. For anyone caught outdoors when a storm like this develops, forecasters recommend seeking the nearest solid structure rather than a vehicle, since even a parked car offers only limited protection against stones large enough to shatter glass on impact.
This article was produced with the assistance of AI and reviewed by Morning Overview editors.
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