It spread over an incredible 768 kilometres.
A lightning bolt in the southern United States that spread 768 kilometres across the sky has broken the record for the longest single flash, the UN's World Meteorological Organization (WMO) said on Tuesday.
It spread from Mississippi and Louisiana to Texas on 29 April 2020, covering a distance equivalent to between London and Hamburg, the UN weather agency added.
This new record is 60 kilometres longer than the previous record of 709 kilometres from a lighting bolt that flashed across parts of southern Brazil on 31 October 2018.
Another lightning record was broken in 2020, the global weather agency added, that of the longest duration of a lightning flash.
A bolt developed for 17.1 seconds during a thunderstorm over Uruguay and northern Argentina on 18 June 2020. The previous record was 16.73 seconds -- a flash that developed continuously over northern Argentina on 4 March 2019.
“These are extraordinary records from single lightning flash events," said Professor Randall Cerveny, who verifies global weather records for the WMO.
"It is likely that even greater extremes still exist, and that we will be able to observe them as lightning detection technology improves."
The record-breaking bolts occurred in hotspots of North and South America where "mega flashes" can occur -- in the Great Plains and in the La Plata basin.
Scientists warned that the extraordinary lightning flashes showed that people should be careful when they hear thunder and head for cover in substantial buildings or fully-covered vehicles.
“These extremely large and long-duration lightning events were not isolated but happened during active thunderstorms. Any time there is thunder heard it is time to reach a lightning-safe place," said lightning specialist Ron Holle in the statement released by WMO.
The new findings were published in the Bulletin of the American Meteorological Society.