Lightning hits the Earth roughly 100 times per second, or 8 million times a day. Yet there's still a lot we don't know about it, and as new research enlightens us, it's worth reflecting on how incredible — and dangerous — lightning can be.

The longest lightning strike known to science burned for 321 kilometers (199.5 miles) over Oklahoma in 2007, according to a new report by the U.N. World Meteorological Organization (WMO). Lightning tends to strike relatively near its parent storm, but it can also leap surprisingly far away. "Bolts from the blue" are known to travel 40 kilometers (25 miles) or more, for example, and cloud flashes have been recorded spanning up to 190 km (118 miles). This is the first time lightning records have been included in the WMO's official archive of weather and climate extremes.

In addition to the longest-distance strike, the WMO researchers have also identified the longest-duration lightning event on record: a 2012 flash over southern France that lasted continuously for a shocking 7.74 seconds.

As better technology and monitoring reveal previously unknown extremes like these, the researchers say it's time for the American Meteorological Society (AMS) to update its formal definition of lightning. Since the 2012 flash lasted nearly 8 seconds, for instance, it no longer seems fair to limit lightning to a 1-second event.

"[T]he committee has unanimously recommended amendment of the AMS Glossary of Meteorology definition of lightning discharge as a 'series of electrical processes taking place within 1 second' by removing the phrase 'within one second' and replacing with 'continuously,'" the researchers write.

lightning strikes Thunder offers a helpful warning, but we can't rely on sound alone to stay safe from lightning. (Photo: John Fowler/Flickr)

Aside from illustrating the awesome power of thunderstorms, these new world records also provide an important reminder of how far their life-threatening influence can reach. Lightning kills thousands of people around the world every year, especially in poor, tropical parts of the world, but also in wealthier countries. The U.S. suffers an average of 49 lightning fatalities per year, according to statistics kept by the National Oceanic and Atmospheric Administration (NOAA).

"Lightning is a major weather hazard that claims many lives each year," WMO Secretary-General Petteri Taalas says in a statement. "Improvements in detecting and monitoring these extreme events will help us improve public safety."

Most U.S. lightning deaths occur during outdoor leisure, NOAA reports, especially water-related activities such as fishing, boating, swimming or visiting a beach. Sporting events and social gatherings also lure many people to overlook or tolerate the risks of lightning, as do some outdoor jobs like construction work and farming.

As lightning heats up the air to about 20,000 degrees Celsius — three times hotter than the surface of the sun — it causes gases to explode, triggering the sound we call thunder. Humans can hear thunder up to 25 miles away, and given how far lightning can travel, heeding this natural warning is the least we can do to stay safe during thunderstorms. (It might be wise to keep a good weather app on your phone, too.)

"This investigation highlights the fact that, because of continued improvements in meteorology and climatology technology and analysis, climate experts can now monitor and detect weather events such as specific lightning flashes in much greater detail than ever before," says WMO researcher and study co-author Randall Cerveny. "The end result reinforces critical safety information regarding lightning, specifically that lightning flashes can travel huge distances from their parent thunderstorms.

"Our experts' best advice," he adds, is "'When thunder roars, go indoors.'"

While these newly reported extremes are impressive, we probably still don't know the limits of what lightning can do. "It is possible, indeed likely," the researchers write, "that greater extremes can and have occurred."

Russell McLendon ( @russmclendon ) writes about humans and other wildlife.