text: Hailstones do cause injury if they're large enough.\n\nSmaller ones are less harmful.  The reason lies in the density and air resistance difference between a penny and a hailstone.\n\nA penny weighs about 3 grams.  A comparable hailstone would have to be at least .75 inches in diameter to be comparable in mass, and will have more wind resistance as it falls.  \n\nCheck out this link regarding hailstone injury