Question 1 of 15
What is required for large hail to form?
Why: The stronger the updraft, the longer a stone stays in the growth zone and the bigger it gets.
Question 2 of 15
What hail diameter does the National Weather Service consider severe?
Why: One inch, about the size of a quarter, is the severe threshold that can trigger a severe thunderstorm warning.
Question 3 of 15
Hailstones grow by which process?
Why: Supercooled liquid water freezes onto the stone as it is carried through the storm, adding layer after layer.
Question 4 of 15
Why do many hailstones show onion-like layers when cut open?
Why: Clear layers form in wet growth, cloudy layers in dry growth, recording the stone's trip through the storm.
Question 5 of 15
Where did the largest US hailstone by diameter fall?
Why: The Vivian, South Dakota stone of July 23, 2010 measured 8 inches across and weighed nearly 2 pounds.
Question 6 of 15
What is graupel?
Why: Graupel is soft and crumbles easily. It is not classified as hail despite looking like tiny white pellets.
Question 7 of 15
Which region is nicknamed Hail Alley?
Why: High plains elevation puts the freezing level closer to the ground, so stones melt less on the way down.
Question 8 of 15
Roughly how fast can a softball-sized hailstone fall?
Why: Terminal velocity climbs with size. The largest stones can exceed 100 mph, which is why they destroy roofs.
Question 9 of 15
In which season does most damaging US hail occur?
Why: Hail peaks with the severe storm season, when strong updrafts are most common.
Question 10 of 15
Can hail fall on a hot summer day?
Why: Hail forms miles up where it is well below freezing, then falls fast enough to survive the warm air below.
Question 11 of 15
What is the greenish sky sometimes seen before a hailstorm caused by?
Why: The green tint comes from how sunlight is filtered by an unusually deep, water-laden storm.
Question 12 of 15
What is the best action when hail begins while driving?
Why: Stay in the vehicle. Trees can drop limbs, and windshields are laminated so they usually crack rather than shatter.
Question 13 of 15
Which crop losses make hail especially costly?
Why: A single storm can wipe out a season of Plains grain in minutes, which is why crop hail insurance exists.
Question 14 of 15
Do hail cannons actually prevent hail?
Why: Shock waves from a ground device cannot meaningfully alter processes happening miles overhead.
Question 15 of 15
What is the heaviest hailstone ever reliably recorded worldwide?
Why: A stone weighing about 1.02 kg fell in the Gopalganj district of Bangladesh during a deadly 1986 hailstorm.