Which factor contributes to the severity of damage caused by hail?

Wind speed significantly contributes to the severity of damage caused by hail because it can increase the impact force of the hailstones as they strike a surface. When hailstones fall, they gain speed due to gravity, but when there is also substantial wind, this can create an additional horizontal force, causing the hail to hit structures, vehicles, or vegetation with greater energy. This increased impact can lead to more extensive damage to roofs, siding, windows, and cars.

The size of the hail can also be a critical factor because larger hailstones inherently possess more mass and thus more potential for causing damage upon impact. However, the correct answer emphasizes wind speed, as it amplifies the damage potential by altering how hail impacts surfaces. Other factors like humidity and temperature can affect the overall storm environment and the formation of hail but do not directly influence the damage severity as immediately as wind speed does.