GENEVA: A new world record for the longest distance lightning flash was declared on Thursday — a megaflash that stretched for 829 kilometres across the United States.

The huge flash occurred on Oct 22, 2017, from eastern Texas to near Kansas City, the World Meteorological Orga­nisation said.

The United Nations WMO weather agency said the megaflash underlined the epic power of lightning — and how flashes can pose dangers far from the original storm.

The previous record, also observed in the United States, happened on April 29, 2020, between Mississippi and Texas, with a lightning flash of 768 kilometres. It was certified as a record in 2022.

Both the previous and new records have a margin of error of plus or minus eight kilometres.

The 2017 storm produced several huge flashes. Three were analysed and were enough to formulate a ground-breaking definition of megaflash lightning.

Going back and re-examining the data from the landmark storm led to the discovery of a hitherto overlooked megaflash that was bigger than the one in 2020.

Bolt from the blue

“Lightning can travel quite long distances away from the parent thunderstorm,” Randall Cerveny, the WMO’s rapporteur for weather and climate extremes, said.

“That is why some people talk of a `bolt from the blue’ _ a lightning flash that seemingly comes out of the clear sky.”

Cerveny, a professor of geographical sciences at Arizona State University, established the WMO’s World Weather and Climate Extremes Archive in 2007.

It logs global records for temperature, pressure, rainfall, hail, aridity, wind, lightning and weather-related mortality.

An 11-member committee of experts based in the United States, Brazil, Germany, Spain, Nepal and Israel certified the new record.

Satellite-based lightning mapping has only been up and running since 2016 _ too short a timeframe to determine patterns or trends in intensity, location or frequency.

“Give us another decade or so of data and we can start to address that,” Cerveny said.

Published in Dawn, Aug 1st, 2025