Interactive Explainer
What causes hail?
Hail forms inside strong thunderstorms when ice embryos get carried upward again and again through regions full of supercooled liquid water. Each trip can add another frozen layer until the stone becomes too heavy for the storm to hold up.
Hail needs a thunderstorm strong enough to keep lifting growing ice through very cold, very wet air.
A hailstone often grows in loops, freezing new coatings each time it passes through a fresh pocket of supercooled water.
Large stones require unusually powerful updrafts, a long growth path, and enough cold air to stop the stone from melting too early.
Try It Yourself
Hail Growth Lab
Strengthen the updraft, deepen the freezing layer, or add more supercooled water to see when a soft pellet becomes a layered hailstone with real damaging potential.
What changes the fastest
What is driving the result
The Big Idea
What is actually happening?
An interactive explainer about how thunderstorm updrafts recycle ice through supercooled water, why hailstones grow in layers, and why some stones melt before they ever reach the ground.
A storm first makes a small ice embryo
Frozen raindrops, graupel, or tiny ice particles provide the first solid core a hailstone can build around.
The updraft throws the embryo upward
A strong thunderstorm can keep lifting the growing stone back into colder, wetter parts of the cloud instead of letting it fall out immediately.
Supercooled droplets freeze onto the stone
Liquid water can exist below freezing inside storm clouds. When it hits the ice embryo, it freezes and thickens the hailstone.
Eventually the storm loses the battle
Once the hailstone becomes too heavy, or the updraft weakens, the stone falls toward the ground and may melt partly on the way down.
Good Follow-Up Questions
The details are where this gets interesting
The short answer helps, but the edge cases and comparisons are what make the topic memorable.
Large hail is mostly an updraft story
A storm needs strong vertical motion to keep recycling the stone long enough for major growth.
A hailstone records its own history
Cutting one open often reveals layers that reflect different freezing conditions during repeated trips through the storm.
Surface damage and storm strength are not perfectly matched
A severe storm can still produce smaller hail if the lower atmosphere melts the stones before they reach the ground.
Compare Scenes
The same thunderstorm can produce very different hail outcomes
The size depends on how often the stone gets recycled and how much melting happens before it falls out.
Fast Answers
Questions people usually ask next
Good science pages should answer the obvious follow-ups without making the reader hunt for them.