On This Date: Washington, D.C. Record Hail Was Radioactive
On May 26, 1953, 72 years ago today, a severe thunderstorm dumped hail up to 4.15 inches in diameter on the southeast side of Washington, D.C., according to the U.S. Weather Bureau (now, National Weather Service) and weather historian Christopher Burt.
Roughly the size of a softball, this remains the largest hail on record for the District of Columbia. NOAA's database has only one other D.C. hail event of baseball size (2.75 inches) from July 10, 1975. (There is a report of 5-inch diameter hail on July 2, 1968 just northeast of Dulles Airport in Loudoun County, Virginia.)
You'd think a record hailstorm in the Nation's Capital would be the headline of this story. But that's not the most bizarre aspect of it.
At that time, the U.S. conducted some atomic tests in the Desert Southwest. One such test in Frenchman Flat, Nevada, happened only 29 hours before the D.C. hailstorm. The U.S. Navy's chief hydrographer, J. B. Cochran wondered whether the hail had elevated levels of radioactivity from the test.
Scientists captured some of the hailstones atop the U.S. Navy Hydrographic Office in nearby Suitland, Maryland, along with some gravel atop the roof. In a study released in 1954, they measured elevated radiation levels in both the gravel atop the roof and especially in the hailstones, though levels were still considered "relatively small" and easily reduced by washing in distilled water.
How did they know it came from the test site?
The upper air wind pattern with a strong jet stream over Nevada spread the material lofted up to 40,000 feet from the atomic test over the Northern Plains, Great Lakes, and eventually into the mid-Atlantic states. "Strong (thunderstorm) updrafts...caused large raindrops and hailstones to be recirculated several times through the contaminated air mass before they fall to earth," the study's authors concluded.
Jonathan Erdman is a senior meteorologist at weather.com and has been covering national and international weather since 1996. Extreme and bizarre weather are his favorite topics. Reach out to him on Bluesky, X (formerly Twitter) and Facebook.
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