Why do hailstones grow big in summer, the hottest time of year?
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After you watchWhy do hailstones grow big in summer, the hottest time of year?
The short answer
Hail can grow in the freezing parts of a thunderstorm even when the ground is warm. Updrafts support ice as it collects supercooled droplets.
Try this next
- Does a fixed pellet stay aloft when the updraft is weaker? Move the updraft slider in the practice cloud. That pellet keeps its size; the separate matched test lets pellets grow.
- Would the same updraft produce the same hail with fewer supercooled droplets? Thought experiment: change the droplet supply while keeping the updraft fixed. The screen keeps the supplies matched, so this new case is not simulated.
Now you — bend it
- What if Change the practice updraft while the pellet stays the same size.Observe whether the model pellet rises or sinks; this control tests support, not final hail size.
- What if Thought experiment: fewer supercooled droplets reach the strong updraft.A longer stay does not guarantee more growth if there is little liquid water to collect.
Can you prove it?In this matched model, the stronger updraft gives a pellet more time to collect ice. — Release both pellets with matching supplies. Compare their growth marks and time in the cloud. Rings and repeated paths are simplified illustrations, not counts of real cloud journeys.
Design your own test:Predict when the fixed-size pellet rises or sinks, then change the updraft and watch.
Explain it to a 6-year-old: Wind inside a storm can hold an ice pellet where chilly drops freeze onto it. A longer stay can let it grow.
The whole story
How it works
A supported ice particle can gain ice from colliding supercooled drops. Stronger updrafts can support larger stones, but water supply, cloud path, and melting also affect hail size.
What people get wrong
The animation uses looping paths and rings as time and growth marks. A real hail layer is not a count of one journey; wet and dry growth produce different-looking ice. Hail can occur outside summer.
The catch
The animation uses looping paths and rings as time and growth marks. A real hail layer is not a count of one journey; wet and dry growth produce different-looking ice. Hail can occur outside summer.
Questions kids ask
Does each ring mean one trip through the cloud?
No. Clear and cloudy layers reflect different freezing conditions. The loops in this model simply show time available for growth.
Can hail happen when the ground is warm?
Hail can grow in the freezing parts of a thunderstorm even when the ground is warm. Updrafts support ice as it collects supercooled droplets.
Does a strong updraft guarantee giant hail?
A supported ice particle can gain ice from colliding supercooled drops. Stronger updrafts can support larger stones, but water supply, cloud path, and melting also affect hail size.
Talk about it
- It is hot out and ice is falling from the sky — guess first, where do you think that ice came from?
- If we sliced a big hailstone in half like an onion, what do you think we would see inside, and why?
- Two storms pass over us on the same day. What might make one drop hail and the other just rain?
For grown-ups
The animation uses looping paths and rings as time and growth marks. A real hail layer is not a count of one journey; wet and dry growth produce different-looking ice. Hail can occur outside summer.
Keep going
What else makes you wonder?
- What is the biggest hailstone that has ever fallen, and how many trips up the cloud did it take to grow that big?
- If you could see inside a storm cloud, how fast would the updraft feel if you were riding it?
- Why do some summer storms make hail while others right next door only make rain?