A bolt of lightning that stretched nearly 800 kilometres across three US states is now the world record holder for longest flash recorded.

The single flash extended 767.9 kilometres across Texas, Louisiana and Mississippi in April 2020, the World Meteorological Organisation said on Monday (US time).

That beat the old record set in 2018 in Brazil of 709 kilometres.

Also in 2020, a single lightning flash over Uruguay and northern Argentina lasted 17.1 seconds, nipping the old time record of 16.7 seconds.

Normally lightning doesn’t stretch further than 15 kilometres and lasts less than a second, said Arizona State University’s Randall Cerveny, who is the chief of records confirmation for the meteorological organisation.

“These two lightning flash records are absolutely extraordinary,” Professor Cerveny said in an email.

Both were cloud-to-cloud, thousands of metres above ground level, so no one was in danger, he said.

These records, which are not linked to climate change, were spotted and confirmed thanks to satellite tracking technology.

Both regions are two of the few places in the world prone to the type of intense storms that can produce what are called “megaflashes”, Professor Cerveny said.