16. What causes hail to form? Hail is caused when raindrops are lifted up into the atmosphere during a thunderstorm and then supercooled by temperatures below freezing, turning them into ice balls, says Dr. Dick Orville of Texas A&M University. "The faster the updraft on these balls of ice, the bigger they can grow," he adds.

16. What causes hail to form?

Hail is caused when raindrops are lifted up into the atmosphere during a thunderstorm and then supercooled by temperatures below freezing, turning them into ice balls, says Dr. Dick Orville of Texas A&M University. "The faster the updraft on these balls of ice, the bigger they can grow," he adds.