Hail is one of the many types of precipitation that falls on this planet we call Earth. In order to know how it forms, we must first understand what it is. Hail is an irregular ball of water ice that has fallen from the sky. They are only produced by the clouds that cause thunderstorms (Cumulonibus clouds). Not too difficult to understand, is it? Well, now that we have defined what hail is, the next thing to discuss is how it forms.
Hail forms when a layer of ice forms around a condensation particle, such as a piece of dust or some other thing for it to condense on. In a storm cloud, there are a lot of violent winds that blow things all over the place. One of these winds is called an Updraft, which is a wind that blows things up higher into the storm cloud. The water that has condensed around the dust particle forms a layer of ice as it rises up. When the Updraft ceases, the ice falls back down to the bottom of the cloud.
This is not the end of the hail-forming process. Often, another updraft will form, and the iceball will be carried up to the top of the cumulonimbus cloud once more. Another layer of ice will form. When the updraft vanishes, the ice falls again. This cycle may repeat multiple times. The constant cycling of up and down motion is what gives different hailstones their various heights. Finally, after a hailstone has become too heavy for the Updraft to push it high in the clouds, the hailstone falls to the ground.
You may have heard of meteorologists basing the severity of the storm by the size of the hailstones it drops. This can be a good way to measure the severity of a storm. This is because if a storm is more powerful, it will have more powerful winds in its storm clouds. If the winds are more powerful, the Updrafts will be as well. Since the updrafts are more powerful, in order to be free from the updrafts and fall to the ground, hailstones will need to be heavier. This makes them accumulate more and more ice layers, which of course increases the size of the hailstorm, and giving meteorologists a good way to measure the power a storm had.
Hailstones are an important form of precipitation. They are as important to life on Earth as rain, sleet, and snow are. They provide water to ecosystems and rivers, and now that you understand the process that goes underway to make them, I hope you will appreciate them as much as I do, and not just look at them as another way your car can be dented!