Hail is the precipitation of balls
or pieces of ice with a diameter of 5 mm to 10 cm (about 0.2 to 4 inches).
Small hail (also called sleet, or ice pellets) has a diameter of less than
5 mm. Because the formation of hail usually requires cumulonimbus or other
convective clouds with strong updrafts, it often accompanies
Large hailstones are often characterized by alternating layers of clear
and opaque ice, caused by irregular rates of freezing. In areas where the
temperature is not far below 0° C (32° F), freezing occurs slowly,
allowing trapped air to escape and producing clear ice. When the hailstone
then moves into a much colder area, freezing occurs quickly, trapping air
and producing a layer of white ice.
Hail is extremely destructive to buildings and crops; if large enough, it
may be dangerous to animals exposed to it. Hailstones about 15 cm (6
inches) in diameter have fallen during thunderstorms in the Middle Western
United States. Hailstorms are most common in the middle latitudes and
usually last around 15 minutes. They ordinarily occur in middle to late
Hail about an
inch larger than stones can broke windshield. Chasers have
witnessed golf ball sized stones about this diameter (see picture below) cannot break glass. It
depends on the hardness of the stones and the angle of the impact.
Occasionally a motorist can get lucky and get hit with a large soft stone
when temperatures aloft are warmer. The soft stones crack apart absorbing
the impact. In this case the stones were rock hard.
Hail Damage to Residences
Hail in the wake of a tornadic super cell thunderstorm. Severe damage
results to residents to include roofing, siding and windows. Even the non
evergreen trees are stripped of all leaves and small limbs.
Deep hail can easily worsen a flash flood
situation. Since ice (hail) floats on water it tends to clog drainage
paths, culverts and grates. In flat country as found in the high plains
states, water, mud and hail combinations begin to cover the roadways fast.
can I prepare for disaster? Hail
Hailstorms are frequent occurrences across the U.S. Most hailstorms
occur during either the spring or fall months, are very localized events,
and don’t cause extensive property damage. However, occasionally
hailstones can reach about 1.5 inches in diameter. When this occurs, they
can cause significant property damage to cars, windows and siding.
When hailstones reach three inches in diameter, they can cause major roof
Consider replacing your roof covering with
roofing material that received a UL impact resistant classification
(UL2218) of Class 4, meets local building code standards and requires
minimal upkeep and maintenance.
Listen to weather updates about hail activity.
Seek shelter immediately if you are caught outdoors – preferably not
under a tree.
Stay indoors until the storm subsides.
Close drapes, blinds or window shades for protection from the
possibility of breaking glass.
Park your vehicle in a garage or under a shelter.
If driving, pull over to the side of the road – preferably under an
overpass or shelter.