The question of whether pea-sized hail causes damage is common, as this size is often the most frequently reported during thunderstorms. Pea-sized hail is an informal meteorological classification describing hailstones approximately one-quarter of an inch (0.25 inches) in diameter. Although hail this small is rarely considered “severe” by weather organizations, which typically reserve that designation for stones one inch or larger, it is not entirely harmless. This article details the property damage risk associated with this common precipitation type.
Defining Pea-Sized Hail
Meteorologists commonly use comparisons to household objects or coins to quickly communicate hail size to the public, and the pea is the smallest of these common benchmarks. A pea-sized stone measures about 6 to 7 millimeters across and falls far short of the three-quarter inch diameter that often triggers the lowest level of “severe” weather warnings. Understanding the physical force of this hail starts with its terminal velocity, the maximum speed the stone reaches as it falls through the atmosphere.
A hailstone’s impact energy is determined by its mass and its speed upon striking the ground. A one-quarter inch stone often falls below 20 miles per hour (mph) under normal conditions. The small mass and relatively low speed mean the kinetic energy of a pea-sized hailstone is minimal compared to larger hail. This low-energy impact is the primary reason that pea-sized hail rarely causes structural damage to most modern building materials.
Impact on Vulnerable Surfaces
Pea-sized hail generally causes minimal to zero damage on robust, impact-resistant surfaces. Standard residential materials like asphalt shingles, tempered glass windows, metal siding, and modern vehicle bodies are manufactured to withstand significantly higher impact forces. On a newer, well-maintained roof, these small stones are most likely to cause only a minor loss of protective surface granules on asphalt shingles over time, which is considered wear rather than immediate functional damage.
The surfaces that are vulnerable are those made of softer, more delicate materials. Tender garden vegetables, newly sprouted plants, and soft foliage can be bruised, torn, or stripped by the sheer volume of small impacts. Cosmetic damage can occur on older or poorly maintained exterior paint finishes, where the impact can chip or scuff the material. Vinyl window screens are also susceptible to minor tears or stretching when subjected to a direct barrage of this small hail. This damage is usually superficial, often healing naturally in plants, but it still represents a loss for agricultural crops.
Environmental Factors That Increase Risk
While the pea-sized hailstone itself possesses little destructive energy, the environmental context of the storm can significantly modify its impact potential.
The most influential factor is wind, which adds a horizontal velocity component to the stone’s downward fall. High winds increase the effective speed of the hail upon impact, which can dramatically increase the force delivered to a surface. This wind effect also changes the angle of impact, turning a straight vertical drop into a driving blow that can affect vertical surfaces like the sides of a car or a house.
The storm’s duration and the volume of the hail fall also determine the overall risk. A prolonged hailstorm allows for a cumulative effect, where repeated, low-force impacts on the same area can eventually cause damage that a single stone could not. If the hail falls at a very high density, the sheer mass can create a “snowplow hail event,” where the ice piles up and blocks city drainage systems.
Lastly, the density of the hailstone itself matters. A solid, hard ice sphere will transfer more force than a softer, slushy stone of the same size, slightly altering the damage threshold.