Hail is a form of precipitation consisting of balls or irregular lumps of ice that form within severe thunderstorms. Strong updrafts carry water droplets high into the atmosphere, where they freeze and grow as they collide with supercooled water. Hailstones range in size from 5 millimeters (about 0.2 inches) to over 15 centimeters (about 6 inches) in diameter. Hail can certainly hurt, with the potential for damage spanning from minor discomfort to serious danger, depending on the size and speed of the descending ice.
The Physics Behind Hail Damage
The destructive power of a hailstone is rooted in the physics of its impact, specifically its kinetic energy. Kinetic energy is determined by the hailstone’s mass and the square of its velocity. This means a small increase in size or speed results in a disproportionately large increase in impact force. The terminal velocity, or maximum falling speed, increases significantly with the hailstone’s diameter.
For instance, a small hailstone of 1 centimeter (0.4 inches) in diameter may fall around 20 miles per hour (9 m/s). However, a larger stone of 8 centimeters (3.1 inches) can reach speeds of 110 miles per hour (48 m/s) or more. Horizontal wind speed can further increase this velocity, adding a sideways component to the impact and enhancing the overall damage potential.
Biological Impact on People and Pets
When hailstones strike a living creature, the resulting injuries vary widely based on the ice mass and speed of impact. Smaller hailstones commonly inflict minor injuries such as bruising, welts, and superficial lacerations. These impacts can cause significant pain and localized swelling on exposed skin.
Larger hailstones, typically those golf-ball size (1.75 inches) or greater, pose a serious physical threat. A direct hit can cause deep, severe lacerations requiring stitches, broken bones, and concussions. In rare cases, the kinetic energy transferred from softball-sized hail has been known to be fatal to humans and animals. Pets and livestock caught in the open are particularly vulnerable, as they are less able to seek immediate, sturdy shelter.
Structural and Property Damage
The physical force of hail translates directly into widespread damage on non-biological targets. Vehicles are frequently affected, with hailstones causing dents across body panels and chipping the paint. Larger hail can shatter windshields and windows. Repeated impacts may also weaken the vehicle’s structural pillars or cause misalignment.
Residential and commercial buildings also suffer extensive consequences, primarily to roofing materials. Hail impacts can dislodge the protective granules on asphalt shingles, leading to cracking, punctures, and accelerated material degradation. This damage compromises the roof’s integrity, creating pathways for water intrusion and eventual structural deterioration. Agricultural losses are also significant, as hailstones can shred foliage and destroy entire fields of crops.