What is hailstone?

A hailstone is like a snowball that grows bigger as it travels through the sky.

Imagine you're playing outside on a cold day and you start rolling a snowball across the yard. Every time it rolls over a patch of snow, it picks up more snow, getting bigger and bigger. That’s kind of what happens to a hailstone inside a cloud.

Inside a big, puffy cloud, there are lots of tiny water droplets. When the air gets cold enough, these droplets freeze into little ice balls. These ice balls then fall back down through the cloud, where they might pick up more water droplets, and get bigger again! This freezing and growing happens many times as the hailstone travels up and down in the cloud.

Sometimes a hailstone can be as small as a pebble, but when it’s really big, it can feel like a rock when it falls to the ground. That’s why you might hear people say, “It felt like someone threw a hailstone at me!”