1Two things hiding inside a storm cloud
It's freezing up top — and the hot ground makes a rising wind
You only need two ideas. Watch each one:
The cloud-top is freezing
A tall storm cloud is warm and sticky down low, but far below freezing up high. Even on a hot day, the very top of the cloud is colder than your freezer.
Hot ground makes air rise
Sun-baked ground heats the air, and warm air shoots upward. That rising column is an updraft — an invisible wind blowing straight up the middle of the cloud.
2Two kinds of updraft
A gentle puff vs a violent blast
Not every storm has the same upward wind. The whole story turns on how strong that updraft is:
The gentle puff
A soft breeze of rising air. An ice pellet drifts down through it and falls out the bottom.
The violent blast
A fierce column of rising air, strong enough to catch a falling pellet and shove it back up.
3Your turn — be the storm's wind
Drag the updraft and feel it push on a pellet
Here's one little ice pellet floating in the cloud. Slide the updraft from a puff to a blast and watch how hard the rising wind pushes back on it — a strong updraft can hold it up high; a weak one lets it sink.
4Now grow a real hailstone
Drop a pellet in and watch it try to grow 🧊
Here's the test. A pellet only grows by looping up to the freezing top, picking up a frozen coat, falling, and getting caught and flung up again — a new layer every loop. Same pellet, two storms. Guess first, then release it.
Guess before you release it
What makes a hailstone grow big — a weak updraft, or a strong one?