Giant hail fell Thursday in Argentina. (Victoria Druetta)

The hail started around 4:30 in the afternoon in Cordoba, Argentina. At first, it was “tiny and fun,” but then it changed. Hailstones larger than tennis balls began to fall from the sky, eventually growing to mammoth size.

Victoria Druetta hurriedly snagged one giant stone that fell in her neighborhood of Carlos Paz, snapped a photo of it and placed it in her freezer.

“The hail lasted 20 minutes. It was kind of scary,” Druetta recalled. “It hit and then exploded and then melted some. It was probably even bigger.”

The stone looks to be up to 18 centimeters in diameter — 7.1 inches — at its largest width, which could be a record for the Southern Hemisphere. The stone’s unusual size made it difficult to measure because of its bumpy surface and because it melted a bit before Druetta put it down on a tape measure.

Videos show the behemoth hail stones landing like small meteors.

Hail can reach this size only if thunderstorm updrafts are strong enough to keep it suspended in the air. That would require vertical winds exceeding 120 mph.

As layers of ice glaze onto the growing stone, erratic winds high in the sky can carry it into dry regions. When that happens, the outside of the stone freezes faster than the inside. This has been shown to produce bizarre protrusions, which grow with each successive pass through the cloud. Once the stone becomes too heavy, it falls out of the cloud, sometimes faster than a major league baseball pitch.

In events like this, each hailstone contains so much water that fewer stones end up forming. That’s why there’s a large gap between where they strike — sometimes landing 20 or more feet apart. In one video, bewildered onlookers hunkered beneath a metal overhang can be heard remarking about “ice the size of sports balls,” calling the spectacle “pure insanity.” The stones shattering on the pavement sent shards flying 15 feet.

Spanning more than 2,500 miles north to south, Argentina has a wide variety of climates — including a severe weather season, which is peaking right now in Southern Hemisphere summer.

Dry air sinking down the east slopes of the Andes meets up with moist flow from the Atlantic Ocean. When the two air masses clash, a battleground can quickly develop. Storms Thursday unleashed torrential rains and damaging winds, flooding streets and whipping up a frenzy. But the real showstopper was the hail.


(Victoria Druetta)

At over 7 inches, Druetta’s stone falls short of the U.S. record holder, an 8-inch hailstone that fell in Vivian, S.D., on July 23, 2010. That one was eight inches across and weighed 1.93 pounds, making it the largest and heaviest to ever occur in the United States. While that appears to be a world record for size, it was not for weight.

The Argentina stone could claim second place for width, as well as be the biggest on record south of the equator. The World Meteorological Organization has not commented yet on this finding.