477-mile-long Horizontal Lightning: Myth or Megaflash?

lightning megaflash
Lightning is seen from the Geostationary Lightning Mapper on NOAA's GOES-16 satellite April 29, 2020. One of the lightning flashes within this thunderstorm complex was found by the World Meteorological Organization to be the longest flash on record, covering a horizontal distance of 477 miles (768 kilometers). NOAA

Shattering previous world records in a mind-zapping display of extreme electricity in a thunderstorm event, Zeus, the ancient Greek god of the sky, has won the gold in two World Meteorological Organization (WMO) lightning "megaflash" categories: the longest single flash and the greatest duration for a single lightning flash. The WMO announced Feb. 1, 2022 that it had certified the two new hair-raising meteorological records.

Aided by the latest satellite technology and after a painstaking data-checking process, the WMO certified that the longest single lightning bolt ever recorded covered a jaw-dropping horizontal distance of 477 miles (768 kilometers) over parts of the southern United States April 29, 2020 — spanning from near Houston, Texas to southeast Mississippi — smashing the previous 440-mile-long (708-kilometer-long) record of a megaflash that zigzagged over southern Brazil on Halloween of 2018.


Setting a new world record for the longest duration of a single lightning flash, a bolt blazed over the skies of Uruguay and northern Argentina for 17.1 seconds June 18, 2020 — outshining the 16.73-second lightning flash that was recorded over northern Argentina March 4, 2019.

Your typical Thundershirt-worthy lightning bolts occur when electricity hops from one cloud to another, or when electricity jumps from a cloud to the ground invoking respect from us Earthlings who sometimes narrowly escape their fiery prongs. Most typical lightning flashes within thunderstorm systems exend only a few miles and since most storm clouds are less than 10 miles (16 kilometers) high, lightning isn't able to travel very far vertical-wise.

But megaflashes aren't your typical lightning bolts. Megaflashes are huge. These high-voltage monsters can strut through high electric fields for hundreds of miles and as the new record demonstrates, set the skies aglow for up to 17.1 seconds as compared to traveling only 2 or 3 miles (3 to 5 kilometers) at 0.2 seconds for a typical flash.

Megaflashes are a result of incredibly intense thunderstorms, called conductive thunderstorms. Scientists are still researching what causes these monster storms, according to Randall Cerveny, professor of geographical sciences at Arizona State University and rapporteur of Weather and Climate Extremes for WMO. “These are extraordinary records from single lightning-flash events. Environmental extremes are living measurements of the power of nature, as well as scientific progress in being able to make such assessments. It is likely that even greater extremes still exist, and that we will be able to observe them as lightning detection technology improves,” he said in Maryland Today.

Researchers measured the latest flashes using satellite-borne, space-based equipment. The record-breaking flashes were discovered by the GOES-16 and GOES-17 satellites that are operated by NASA and the National Oceanic and Atmospheric Administration (NOAA).

As new technology and detection methods continue to improve, lightning scientists believe there are more discoveries on the horizon. Researchers also say they don't know for certain exactly how enormous megaflashes can get, but agree that the latest record-breaking megaflashes are not the final word when it comes to extreme lightning.