The World Meteorological Organization has certified a lightning “megaflash” that stretched 829 kilometres (515 miles) across the U.S. Great Plains as the longest single lightning strike ever recorded. The bolt occurred in October 2017, cutting a horizontal path from eastern Texas to Missouri and lasting 7.39 seconds. A re-analysis of satellite data showed the discharge produced at least 116 cloud-to-ground strikes. Details of the event were published on 31 July in the Bulletin of the American Meteorological Society by a research team led by Georgia Tech applied physicist Michael Peterson. Advances in geostationary-satellite sensors and new processing algorithms made it possible to trace the flash’s full extent, which surpasses the previous 2020 record by about 61 kilometres. Scientists say megaflashes form in long-lived, sprawling thunderstorm systems that create ultra-thin, horizontally extensive charge layers. Although such flashes occur in fewer than 1% of storms, they can ignite wildfires and pose significant safety risks, underscoring the value of continuous satellite monitoring.