US Hailstone and Hailstorm Records

US Hailstone and Hailstorm Records

above: Hail can accumulate to remarkable depths when a storm becomes stationary over one place for a period of time. However, the hail in this image drifted to this depth after being washed into these giant piles in a low-lying area by floodwaters. (Michael Maye, Federal Emergency Management Agency)

Most recently, an investigation into a hailstorm that occurred in Villa Carlos Paz, Cordoba Province, Argentina on February 8, 2018, reported that a hailstone approximately 9.3 inches in diameter may have fallen during a storm there. The Weather Channel's Chris Dolce provides a recap of the event, which was documented in a February paper for the Bulletin of the American Meteorological Society titled “Gargantuan Hail in Argentina.” The authors suggest that hailstones larger than 6 inches in diameter should be classified as “giant.”

If verified, the Argentine hailstone would surpass the American record, an 8-inch diameter stone collected near Vivian, South Dakota on July 23, 2010. (This hailstone was actually said to have been 11 inches in diameter a portion earlier.) However, the Argentine hailstone will likely never become an official record, as its size has only been estimated from video evidence and not from any direct measurements.

On the night of Friday, May 22, 2020, 5.33-inch diameter hailstones were reported in Burburnett, Texas (the same hailstones shown in this Facebook post). As the peak of the U.S. hail season approaches, here is a summary (parts of which appeared in a blog post I published in April 2018) of the costliest and deadliest hailstorms in U.S. history, along with a summary of the largest hailstones observed so far in the U.S. States.

Climatology of snowstorms in the United States

Hailstorms in the United States typically occur during the months of May through August, in contrast to tornado frequency, which peaks in April and May. Snowden D. Flora, in his classic book Hailstones of the United States (1956), analyzed hailstorm events from 1944 to 1953 and found that 20.0% of all hailstones in the United States occurred in May, 24.9% in June, and 21 .9%. in July, and 18.0% in August (in other words, 85% over this four-month period). This finding holds up well alongside a 2007-2010 radar-based climatology study published in the journal Weather and Forecasting, which found that “June is clearly the prime month for severe hail.” (See's summary of the article.)

The parts of the country that are most likely to experience hailstorms (especially those that produce very large hailstones) are somewhat similar to the areas most affected by tornadoes.

The National Weather Service (NWS) uses a variety of analog objects to describe the different sizes of hailstones reported to its offices. see below:

The most expensive snowstorms in the United States

It is now estimated that snowstorms in the United States cause an average of $15 billion in damage to homes, cars, and crops each year. This total has increased significantly in recent decades: the estimate in the 1990s was $1.2 billion annually, and this was itself an increase compared to previous decades. Some factors behind the rapid increase include population growth in hail-prone areas such as Denver and Dallas-Fort Worth and the larger size of many new homes. 2017 was the costliest year to date, when insurance companies reported $22 billion in damages.

A combination of blizzard events in the recent past have resulted in losses of $1 billion or more (2020 USD). Phoenix experienced the most damaging hail storm in U.S. history on October 5, 2010, with a cost of $3.2 billion (adjusted for 2018 dollars). “Some homeowners had to wait more than a year before a licensed contractor was available to repair their roofs,” said meteorologist and operations analyst Brian Wood (Assurant) in a Capital Weather Gang article.

Another very costly storm was the one on April 10, 2001, which cut a wide swath along the I-70 corridor from eastern Kansas into southwestern Illinois and bombarded the St. Louis area. Property damage exceeded $2.5 billion in 2020 dollars.

The St. Louis area was again hit by a series of snowstorms on April 26, 2012, causing $1.6 billion in property damage. The so-called Mayfest Hailstorm, which struck Tarrant and Dallas (Dallas-Fort Worth) counties in Texas on May 5, 1995, caused an estimated $2 billion in damage (USD 2020). The same area was again hit by a devastating hailstorm on March 23, 2016, resulting in $2.2 billion in damage. Again, also in Texas, a hailstorm hit San Antonio on April 16, 2016, causing $1.4 billion in damage, with hailstones the size of grapefruits.

Other $1 billion blizzards include three events that hit Colorado's Front Range. One event occurred between Colorado Springs and Fort Collins on July 11, 1990, causing $1.6 billion in damage (USD 2020). Another impacted the Denver metropolitan area on May 8, 2017, causing an estimated $2.0 billion in damage. Another incident, on July 7, 2009, in Jefferson County, caused $1.2 billion in damage. It should be noted that in some of the above cases, high winds also contributed to the total damage and are not necessarily separated from actual hail damage costs.

The worst snow storms in the United States

Despite the enormous damage to crops and property caused by hailstorms, only three people are known to have died from hail in modern U.S. history:

—Farmer captured in his field near Lubbock, Texas on May 13, 1930;

-A child caught in a cold snap in Fort Collins, Colorado, on July 30, 1979;

-And a boat in Lake Worth, Texas, on March 29, 2000.

The largest hailstones in the United States

The largest officially recognized hailstone ever “captured” in the United States was one that fell near Vivian, South Dakota on July 23, 2010. It measured 8.0 inches in diameter, 18.5 inches in circumference, and weighed 1.9375 pounds. Scott, who collected the monster stone, told me he originally planned to bring the daiquiris out of the cold, but fortunately thought better of it and put it in the freezer before turning it in to the National Weather Service for certification. The hailstone ended up at the National Center for Atmospheric Research (NCAR). Weather magazine has a detailed account of the investigation of this event.

The National Weather Service said of the Vivian hailstones: “The reported value has been evaluated by the National Climate Extreme Panel and found to be accurate. This hailstone is the heaviest and largest diameter hailstone recorded in the United States. When the stone was initially collected after the storm, The stone was 11 inches in diameter, but deteriorated in the observer's refrigerator due to a power outage after the storm.

Other instances of 8-inch diameter hail have been reported in the past but have not been certified. U.S. Weather Bureau Climatological Data by Sections Vol. 22, Part II (April-June 1935) mentions a hailstorm that produced 8-inch diameter hailstones near Ponca City, Oklahoma, on April 17, 1935. A report published in the New York Times on December 27, 1892 (apparently initially printed in The Galveston News reported that 8-inch hail fell at Jay Hill, Texas, during a storm on December 6, 1892.

More recently, what would have been the largest hailstone in U.S. history had it not been for the Vivian Event was a 7.75-inch diameter hailstone collected in Wichita, Kansas, following a storm on September 15, 2010. Note that this occurred less than two months after the Vivian Event!

Below is a list by state of the largest hailstones ever measured for each state. Only a few states maintain an “official” list of such hail-fall records (as listed in SCEC reports), which I list first in the table and then followed by a list of “unofficial” magnitudes by state. I have collected these reports from various sources. If any reader can add to or correct this list, it would be greatly appreciated!

Cold accumulations

Some hailstorms cluster over the same area (with stationary or slow-moving thunderstorms developing), resulting in massive hail accumulations. Hail accumulated 18 inches deep at Seldon, Kansas, on June 3, 1959, perhaps the largest hail accumulation on record in the United States.

As shown in the image above, rainfall during or after a hail storm can cause hail accumulations to accumulate in ditches, stream basins or other low-lying areas, resulting in massive hail piles often several feet deep. Such was the case during a storm south of Clayton, New Mexico, on August 13, 2004, when 12 inches of hail piled up with 5 inches of rain. One of the sewers in the draft became clogged with flow and hail accumulated an astonishing 15 feet behind it!

How climate change could affect cold weather

Little is known about the impact climate change might have on hail climate, although a 2017 paper published in the journal Nature Climate Change used a new modeling approach to estimate changes in hail frequency and size for the period 2014-2070 compared to the period 1971-2000. They concluded, “Although there are expected to be fewer hail days in most regions in the future, an increase in average hail size is expected, with fewer small hail events and a shift toward the occurrence of more larger hailstones.” . This results in an expected increase in the potential for hail damage over most southern regions in the spring, declining to higher latitudes (i.e., north of 50°N) and the Rocky Mountains in the summer. In contrast, a significant reduction in hail frequency and damage potential is expected in the eastern and southeastern regions in the spring and summer due to the large increase in melting that mitigates the gains in hail size from increased buoyancy.

Christopher C. Burt

Weather historian

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