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Seven seconds. That’s how long it took a single lightning flash to streak across the sky from east Texas nearly to Kansas City, Missouri, — a 515-mile journey that has set a new world record for the longest lightning flash ever recorded.
The flash stretched across the sky, hidden within the chaos of a massive storm system spanning from Minnesota to Texas in the early morning hours of Oct. 22, 2017. Scientists didn’t catch it until years later, when satellite data was reanalyzed with improved lightning-detection tools.
A lightning flash that is longer than 60 miles is considered a megaflash. Researchers first discovered them using new lightning-tracking satellites that can measure gargantuan flashes at continental-scale distances.
GOES-16 satellite image recording a record-setting 515-mile lightning mega flash during a storm in October 2017. Red circles mark positively charged branches of the lightning, and blue circles mark negatively charged branches.
“We didn’t even know they existed 10 years ago,” said Randy Cerveny, a professor at Arizona State University and rapporteur of weather extremes for the World Meteorological Organization. “They’re luckily not frequent, but they can occur. To put that in local terms, it would be like a single flash of lightning that stretches from Phoenix all the way to Salt Lake City.”
Now, scientists are working to understand these rare, sprawling bolts — how they form, why they matter and what they can teach us about the atmosphere. This latest record offers a glimpse into how far lightning can travel, why it’s so dangerous and whether something like it could ever happen in Arizona.
What’s a megaflash?
Most lightning flashes are short and localized, rarely stretching beyond 10 miles. But every once in a while — in less than 1% of storms — a single flash can race across the sky for hundreds of miles without ever touching the ground.
Megaflashes form in massive thunderstorms that cover areas as large as the state of New Jersey and often last more than 14 hours. They usually spark in the upper layers of a storm system, as high as 18,000 feet, where conditions allow them to move relatively uninterrupted across the sky.
Larger lightning flashes like megaflashes can happen anywhere, but the Great Plains is a hot spot for them in the United States.
“It’s where you would expect to see severe thunderstorms, storms that produce hail and tornadoes,” Cerveny said. “It’s areas that are plains where you can get a good mixture of dry air meeting moist air with strong winds aloft from a jet stream.”
Lightning strikes over the Dragon Bravo Fire burning on the North Rim of the Grand Canyon on July 15, 2025.
Other hotspots where megaflashes have occurred include the plains in Argentina, China and southern France.
The World Meteorological Organization began tracking extremes in lightning in 2007, but there wasn’t an exact way to measure them. Scientists used ground-based networks of antennas to detect radio signals emitted by lightning and then estimated their location and travel speed based on the time it took for signals to reach other stations in the network.
But those ground-based systems had limits. They couldn’t detect the full scope of lightning flashes that span hundreds of miles. It wasn’t until satellite-based sensors came online that scientists began to grasp their true magnitude, that some bolts don’t just strike — they stretch across the sky.
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What broke the lightning record?
The 515-mile flash surpassed the previous world record by 38 miles. The last record-holder occurred during an April 2020 storm in the southern United States, stretching 477 miles. But scientists didn’t find the new record-setter until they took a second look at satellite data from 2017.
The satellites can document to the millisecond when a lightning flash starts and how far it travels.
The bolt lit up the sky between 4 and 5 a.m. local time, as part of a powerful storm that “basically cut the country in half,” Cerveny said.
Unlike most lightning, which lasts less than a second, this megaflash remained active for more than seven seconds.
“Most people think lightning flashes are instantaneous types of things,” Cerveny said. “Seven seconds in terms of Mother Nature and lightning is a very long time.”
Lightning bolts strike the town of Camp Verde, Ariz., on Aug. 1, 2000. This powerful electrical storm produced damaging winds and heavy rains, causing power outages all over the Verde Valley and throughout Yavapai County.
While this flash holds the record for the farthest reaching, it didn’t usurp the current record-holder for the longest duration. The title belongs to a flash that stretched across Argentina in 2020 for 17.2 seconds.
But scientists have only been aware of megaflashes for a few years, meaning there could be bolts that were much longer in length and duration throughout Earth’s history. This record doesn’t point to a change in the Earth’s atmosphere —yet — just innovations in lightning-tracking technology.
“We’ve only been detecting these things in the last 10 years,” Cerveny said. “This record has nothing to do with climate change in this case. We don’t have a database to find out whether they’re becoming more frequent or not. Hopefully, as time goes on, we can start figuring those things out.”
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Why it matters — especially in Arizona
Randy Cerveny is a professor of geographical sciences at Arizona State University, where he has taught since 1986. He serves as rapporteur on extreme records for the United Nations/World Meteorological Organization.
The discovery underscores why scientists are tracking weather extremes: Understanding megaflashes helps improve forecasting and public safety, and it reminds people not to underestimate a storm.
“The most important thing is safety,” Cerveny said. “It demonstrates that lightning can travel very far away from its parent thunderstorm, and people need to be aware of that and take safety precautions.”
Most lightning deaths and injuries in the U.S. happen before or after the heart of a storm, not at its peak, because people return outdoors too soon. The National Weather Service recommends waiting 30 minutes after a storm passes before resuming outdoor activities.
While megaflares are too high in the atmosphere to hit the ground, there are lightning bolts that can touch land tens of miles away from where the storm is.
“The expression of a bolt out of the blue has some meaning behind it,” Cerveny said. “You don’t have to have anything above you, but you could get struck by lightning.”
Arizona hasn’t experienced a confirmed megaflash since scientists began tracking them. But that doesn’t mean one can’t happen here. Cerveny believes there is potential during the monsoon of experiencing a megaflash.
“Here in the desert, where everything is so flat, it’s a major problem because when you’re outside, lightning can kick off,” Cerveny said. “It may not be a megaflash, but it can hit a long way away from where the storm is.”
But megaflashes are a mystery. Scientists are still learning how they form compared to average lightning flashes.
“There’s a lot of debate as to what exactly causes these things, and that’s to be expected,” Cerveny said. “We haven’t been charting them that long. That’s one of the cool things about science; we don’t have all the answers yet. We’re still learning new things.”
Hayleigh Evans writes about extreme weather and related topics for The Arizona Republic and azcentral.com. Email her with story tips at hayleigh.evans@arizonarepublic.com.
This article originally appeared on Arizona Republic: ASU scientist confirms new record for largest lightning flash
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