The combination of gravity & a downward wind known as a downburst can propel a hailstone at speeds upwards of 90 mph.
The largest hailstone ever recorded fell in Aberdeen, SD on July 23, 2010. It was 8 inches in diameter and weighed nearly 2 lbs.
There are approximately 3,000 hailstorms annually in the United States, resulting in average insured losses of $1.6 billion.
Metal panels should be installed over continuous decking and one of the acceptable sealed deck water underlayment options. Installing over existing roofing material increases the potential of damage from hail.