Hail formation requires environments of strong, upward motion of air within the parent thunderstorm (similar to tornadoes) and lowered heights of the freezing level. In the mid-latitudes, hail forms near the interiors of continents, while, in the tropics, it tends to be confined to high elevations.
Hail falls when it becomes heavy enough to overcome the strength of the thunderstorm updraft and is pulled toward the earth by gravity. Smaller hailstones can be blown away from the updraft by horizontal winds, so larger hail typically falls closer to the updraft than smaller hail.
When a SEVERE THUNDERSTORM WARNING is issued, large hail may pelt you, your home, your pets, and your property. These warnings are issued when a severe thunderstorm is indicated by radar, or reported by a reliable source. You should move to a safe place immediately.