Sleet and hail are both forms of frozen precipitation that occur in the atmosphere. Sleet is formed when snow melts as it falls through warmer air, then re-freezes as it passes through colder air. This results in small pellets of ice that fall to the ground. Hail is formed when rain droplets are lifted high into the atmosphere and freeze multiple times, forming a larger and more solid piece of ice. Hail is usually much larger than sleet, measuring anywhere from a few millimeters to several centimeters in diameter. Sleet and hail can both cause damage to property and crops, but hail is often more destructive due to its larger size.
Difference Between Sleet And Hail
tl;dr
Sleet is formed from melted snow that re-freezes in colder air, while hail is formed from rain droplets that freeze multiple times, resulting in larger pieces of ice.