Longest lightning flash

The greatest horizontal distance covered by a single lightning flash (or "megaflash") is 829 km (515 mi), give or take 8 km (5 mi), between eastern Texas to near Kansas City in Missouri, USA, on 22 October 2017. The event was ratified by the World Meteorological Organization on 31 July 2025.

The lightning discharge, which occurred over the Great Plains (an area renowned for its tempestuous weather), crossed a distance akin to that between Paris, France, and Venice, Italy or roughly the entire length of New Zealand's South Island. In a car, it would take up to nine hours to cover this distance or 90 minutes in a standard commercial airliner.

This surpassed the previous record of 768 km, plus or minus 8 km (477.2 mi, plus or minus 5 mi), crossing the US states of Mississippi, Louisiana and Texas, on 29 April 2020, as verified by the World Meteorological Organization on 1 February 2022. This latest megaflash was previously overlooked, hence the event in 2020 taking the title, but a recent reanalysis of the storm using satellite-imagery data brought it to light.

For context, the typical length of a lightning bolt is around 9 km (5.5 mi) or below. Showing how far we have come in measuring the phenomenon of megaflashes, in 1956 meteorologist Myron Ligda observed and recorded a lightning flash, using radar, that covered a horizontal distance of 149 km (93 mi) inside clouds.