515-Mile-Long ‘Megaflash’ of Lightning Sets a New World Record, Spanning Eastern Texas to West-Central Missouri

In October 2017, lightning stretched across multiple Great Plains states, and a weather satellite captured the event

Sarah Kuta | Daily Correspondent

July 31, 2025

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In October 2017, lightning flashed across the sky in America’s heartland. But this wasn’t your average storm. The single, enormous bolt—known as a “megaflash”—stretched across multiple states, from eastern Texas to west-central Missouri, covering a total distance of 515 miles.

Now, experts say that lightning flash was the longest ever documented. The World Meteorological Organization, the United Nations agency that maintains official records of global, hemispheric and regional extremes, announced the new world record in a July 31 paper in the Bulletin of the American Meteorological Society.

The October 2017 flash beat the previous world record—a 477-mile-long bolt above the Great Plains in April 2020—by 38 miles. It lit up the sky across an area that’s five times larger than the state of Massachusetts, illuminating parts of Texas, Oklahoma, Arkansas, Kansas and Missouri at the same time, reports the Washington Post’s Matthew Cappucci.

Technological advances have made it easier for scientists to study lightning flashes in recent years. The October 2017 event, for example, was recorded using GOES-16, a weather satellite run by NASA and the National Oceanic and Atmospheric Administration (NOAA).

The device, one in a series of geostationary environmental satellites, takes continuous lightning measurements while in orbit. It might detect as many as one million lightning bolts each day. This capability is a “major advance” for researchers, who previously relied on ground-based sensors to study these flashes, says lead author Michael Peterson, an atmospheric scientist at the Georgia Institute of Technology, in a statement.

“We are now at a point where most of the global megaflash hotspots are covered by a geostationary satellite, and data processing techniques have improved to properly represent flashes in the vast quantity of observational data at all scales,” he adds.

“Megaflashes”—classified as bolts that span more than 60 miles—remain rare and mysterious, and scientists are still trying to understand them. The majority of thunderstorms are shorter than ten miles in height, so megaflashes extend horizontally over a wide area of ground.

Though researchers have many unanswered questions, they do know that less than 1 percent of thunderstorms produce megaflashes. These phenomena are often spurred by large, powerful storms that have typically been developing for at least 14 hours and can cover an area the size of New Jersey. Many of these huge storms originate in the south-central Great Plains, often arising when several smaller storms join together to create one massive storm system, reports Scientific American’s Emma R. Hasson.

Although megaflashes travel horizontally, they also emit lightning bolts that strike the ground below. The October 2017 megaflash, for instance, produced more than 116 of these offshoots over the course of its seven-second duration, per Scientific American. On average, however, megaflashes produce five to seven ground-striking branches, according to the statement.

To the casual observer, a megaflash can be perplexing. Often, they seem to appear out of nowhere, sparking through clear skies. But, like any other lightning, this type of flash “actually does come from a thunderstorm … from a very great distance,” says study co-author Randy Cerveny, the World Meteorological Organization’s rapporteur of weather and climate extremes and a meteorologist at Arizona State University, to the Washington Post.

“These megaflashes can travel immense distances from their origin point,” he adds.

Because of this, they can also be dangerous. Members of the public may not realize they’re at risk of being struck by lightning, especially in the minutes after the storm’s peak has passed. So far in 2025, 13 people in the United States have been killed by lightning, according to the National Weather Service.

“The storm that produces a lightning strike doesn’t have to be over the top of you,” says Cerveny in the statement.

For now, megaflashes remain relatively uncommon. But scientists might document even more of them moving forward, now that they’ve got new tools at their disposal.

“Mother Nature is always showing us new, interesting things,” Peterson tells WXIA-TV’s Melissa Nord and Reems Landreth. “So with these new satellites that are continuously monitoring, looking at all the weather hazards around us … it’s just a matter of time where if there’s something new to see, we’re going to eventually see it.”

Sarah Kuta | Read More

Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.