Hail is formed in the atmosphere when updrafts transport raindrops into extremely cold regions of a storm cloud.

The formation of hail is a captivating process that occurs within thunderstorm clouds, particularly in cumulonimbus clouds. These towering, anvil-shaped clouds are capable of generating severe weather phenomena, including hail. The process begins when strong updrafts within the storm cloud lift raindrops into colder areas of the cloud, where the temperatures fall below freezing. In these frigid conditions, the raindrops freeze into ice pellets.

As these ice pellets are subjected to turbulent air currents, they are carried both upwards and downwards within the cloud. During this journey, they encounter supercooled water, which remains in liquid form despite being below its freezing point. When the supercooled water contacts the ice pellets, it rapidly freezes upon them, causing the pellets to accumulate additional layers of ice. This process is known as accretion.

Each time a hailstone is lifted upwards, more layers of ice are added to its structure. The hailstone continues to grow until it becomes too heavy for the updrafts to support, at which point it descends to the ground as hail. The size of the hailstone upon reaching the surface is influenced by the strength of the updrafts and the availability of supercooled water. Hailstones can vary significantly in size, ranging from small peas to large grapefruits.

The internal layers of a hailstone resemble the rings of a tree, providing insight into the hailstone’s journey within the storm cloud. A hailstone with numerous thin layers indicates it has been carried up and down within the cloud many times, whereas a hailstone with fewer, thicker layers suggests it has made fewer trips. This remarkable process highlights the complex and powerful forces at play within our atmosphere.