Lightning:  Fact, Myths and Misnomers

"How likely am I to be struck by lightning?" The facts are that the average annual per capita strike rate in the United States is around 1 in 600,000, and there are are 7.7 casualties per million people per 100 million flashes. The odds of being struck vary considerably across the nation and depend largely upon location, climatology, and exposure.

If you live in an area such as Central Florida where thunderstorms are common, you are more exposed and at greater risk to be struck by lightning if you were along the Pacific Coast, where they are uncommon. If you spend more time outside, either on the job or in leisure activities, you have a greater exposure and risk to be struck by lightning. In fact, people living in low threat areas that spend little time outside may have a higher chance to win the lottery than being struck by lightning!

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Animated Lightning

How far away is the lightning?
 
The FLASH to BANG method provides a best guess estimate:
1...When you see the FLASH
2...Count the number of seconds to the BANG of thunder,
3...Divide this number by 5,
4...And this gives you the MILES the lighting is away from you.

The Flash to Bang method is a use of an approximation of the speed of sound associated with lightning. The widely varying air densities in the atmosphere, influenced by variable temperatures and moisture content, will enhance and retard sound travel. It is this variation in air density through which the sound of thunder travels that accounts for the rumble of thunder.

Is Lightning an Indicator of Severity?

Lightning polarity and flash rate jumps have increasingly become assessments of thunderstorms severity. Studies nationwide attest to the significance in analysis of both of these trends. Positive polarity cloud to ground (CG) lightning strikes is a first indicator, followed by flash rates jumps and a switch to negative polarity dominance. Thunderstorms have been identified to produce severe weather elements immediately preceding the switch to negative CG lightning.

Lightning Density 

Flash Density in Alabama

Frequency Rate of Lightning Strikes

The term “severe lightning” is a common but invalid descriptor of lightning, as there is no simple way to compare the intensity of one bolt to another. Here are some usual numbers associated with lightning bolts: 54,000 degrees F; 100 kiloAmperes (thousand); 1 gigavolts (billion); and 1 terawatt (trillion). When it comes down to it, all lightning is severe! What is measurable by observers, and useful for meteorologists, is the frequency of lightning. A rate of 1 to 3 flashes per minute (FPM) is that of an occasional nature; 4 to 11 per minute is frequent; and, 12 or more strikes per minute (1+ every 5 seconds, over a full minute time duration) is continuous or excessive. Generally speaking, the higher the frequency, the stronger the updraft. Continuous lightning is often associated with a severe thunderstorm; and when considered in light of the flash rate jump study above, can provide insight into the potential severity of a thunderstorm.

 

Heat Lightning

Heat lightning is a misnomer. While lightning can occur outside of thunderstorms in dust storms, volcanic eruptions, and massive updrafts from intense forest fires, heat lightning does not occur. What some people call "heat lightning" is actually lightning illuminating the sky from thunderstorms far over the horizon or otherwise unseen, from which no thunder is heard. Terrain, wind, precipitation, the atmosphere itself and shear distance are all factors in whether or not thunder will be heard when a flash of lightning is observed. Lightning just simply doesn't happen out of hot, thin air!

 

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Lightning

 

Other Important Information

Remember, lightning does not make a thunderstorms severe.  By definition, every thunderstorm has lightning in it.

Lightning is one of the most dangerous aspects of a thunderstorm. Lightning can strike up to 10 miles from the main area of the thunderstorm. That is about the distance you can hear thunder from the storm. Whether or not you can see the actual lightning flash, if you can hear thunder, you are at risk of being struck. Because of this, the National Weather Service has adopted the following the motto, “When Thunder Roars, Go Indoors . . .and stay there at least 30 minutes after the last clap of thunder.”

 


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