Overview

• The WMO Committee on Meteorological and Climatic Extremes officially recognized the 829-km lightning flash on July 31, 2025, certifying it as the longest ever measured with an 8-km margin of error.
• The megaflash traversed from eastern Texas to near Kansas City, Missouri during a storm on October 22, 2017.
• NOAA’s GOES-16 satellite provided continuous lightning mapping data that enabled scientists to precisely measure the flash.
• Megaflashes over 100 km occur in fewer than 1% of long-duration, electrically active storms and reveal gaps in understanding horizontal lightning propagation.
• Researchers advise waiting at least 30 minutes after the last thunder before resuming outdoor activity to guard against distant strikes.