Hailstorms Across the Nation
An Atlas about Hail and Its Damages

Stanley A. Changnon
Illinois State Water Survey
David Changnon
Northern Illinois University
Steven D. Hilberg
Midwestern Regional Climate Center

Illinois State Water Survey
Champaign, Illinois

This atlas addresses the climatology of hail in the United States, based on 80 years of data, observations and damage assessments gathered and prepared by numerous sources.

The lee side of the Rocky Mountains, namely eastern Colorado and adjacent central high plains, has the nation's greatest hail frequency, the greatest hail intensity with the largest average hailstones, the highest average number of hailstones, and the longest hail durations. Winds with hail storms also tend to be strongest on the nation's central and southern high plains, including eastern Colorado, an area where property-hail damage is the nation's highest. The risk of property damage due to hail is highest in Colorado and Kansas, and the risk of crop due to hail is the highest in Colorado, Montana and Wyoming.

This atlas of hailstorms across the nation has addressed
sed all the key aspects of the climatology of hail. The 
key findings include:
-- The nation’s areas of greatest hail frequency are along and just east of the central Rocky Mountains where point averages vary from 6 to 12 hail days per year. -- The lee of the central Rocky Mountains has the nation’s greatest hail intensity with the largest average stone sizes, the greatest average number of hailstones, and longest hail durations when it hails. -- The nation’s lowest hail intensities are found in the southeastern U.S. (Florida), and in the southwest (Arizona and California). -- Winds with hail tend to be strongest in the central and southern High Plains, making property-hail intensity highest in an area including Nebraska, Kansas, Oklahoma, and north Texas. -- Hail risk to crops and property is characterized by enormous variability in both space and time. -- The risk of property damage across the nation varies from a low value of 1 in the southeast to a high of 50 (Colorado, Kansas), and the risk of crop damage varies from a low of 1 in the eastern Midwest and East to a high of 20 in the western High Plains (Montana, Wyoming, and Colorado). -- The intensity of hailfalls changes rapidly across short distances, and average intensity values, and risk of hail damage, significantly differ spatially in most states. -- Hail that is damaging to crops differs from that damaging to property, in that various vulnerable crops are damaged by small stones, whereas property damage occurs only when hailstones are 0.75 inch or larger. -- Exceptionally large hailstones, those exceeding 2 inches in diameter, can occur anywhere it hails in the U.S., but are most frequent in southeastern Wyoming (once every five years) and least frequent in the low hail frequency areas (only once every 100 years or less often at a given point). -- There is great variation in the dimensions of hail damage, with most damages occurring in 5 to 10 percent of all storms, and most losses occurring in only a small fraction of an area experiencing hail on a given date. -- Time changes in hail frequency and crop-hail intensity are quite large with a tendency for low hail incidence in 60 to 80 percent of the years, and exceptionally large losses in 5 to 15 percent of the years. -- The temporal variability of hail loss is greater in the High Plains states than in states in the Midwest, East, or West. -- The magnitude and frequency of hail shifts up and down randomly over time, but the primary spatial features of hail (areas of extremely high or low incidence of hail in a region) persist from decade to decade. -- Prediction of future trends in crop-hail losses for individual states, as trending up or down over the following three to five years, is accurate 80 percent of the time. -- Extremely damaging hailstorms to property show an upward trend with time, and the two most damaging storms in the U.S. occurred since 2000. The nationwide trends in crop-hail losses, in property-hail losses, and in the number of hail days all show downward trends for the 1950-present period. -- Average annual hail losses are $852 million for property and $581 million for crops, a national total of $1.433 billion. On going demographic shifts in the nation’s urban areas with rapidly growing metropolitan areas have increased the potential for costly losses from hailstorms. During the 1951-1970 period, property hail losses represented 46 percent of the nation’s total hail losses (54 percent were crop losses). In the 1981-2000 period, property losses grew and exceeded crop-hail losses and had become 61 percent of the of the national total losses to crops and property.
A storm in a rural area of Illinois is producing 1.5 
inch hailstones and heavy rain. A hailstone has just 
landed in the water in a roadside ditch, creating a 
large splash (15 inches high), illustrating the force 
of large hailstones.
For more hailstorm climatology for Colorado and across the nation, click on the link below:
Hailstorms Across the Nation

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