Lightning Facts

• The maximum distance you can hear thunder is as short as two (2) miles and seldom exceeds twelve (12) miles. Many factors contribute to this wide range, some of which are wind speed, wind direction, terrain, ambient noise and the origin of the return stroke.  

• Sound is generated along the length of the lightning channel as the atmosphere is heated by the electrical discharge to the order of 55,000 degrees F (5 times the temperature of the surface of the sun). This compresses the surrounding  air producing a shock wave, which rapidly decays to a sound pressure wave as it propagates away from the lightning channel.

• The average lightning bolt is 6-8 miles  long and can easily travel 25 to 40 miles horizontally prior to turning downward toward the ground.  In October 2001, the visual lightning detection system measured a single bolt that traveled from Waco to Fort Worth and then Dallas, Texas – a total distance of more than 110 miles

• It is almost soothing to hear the low rumble of thunder off in the distance as a storm approaches, yet the very sound of thunder indicates that you are in immediate danger. The forward and backward reach of lightning far outruns your ability to hear its thunder.   When you hear thunder (even faint thunder) you are in danger of a lightning strike. When the leading edge of a thunderstorm is within 10 miles you are at immediate risk due to lightning's out reach. In fact, many lightning deaths and injuries occur with clear skies directly overhead.  Example

• Many cloud-to-ground lightning flashes have forked or multiple attachment points to earth. Tests carried out in the US and Japan verify this finding in at least half of negative flashes and more than 70% of positive flashes. Many lightning detectors cannot acquire accurate information about these multiple ground lightning attachments.

• Lightning can travel over the surface of the ground and through the ground. The ground surface can be lethal for up to 60 feet radius or more from the point of contact.  This also includes a ground rod as the point of contact.  In water, the lethal radius is about 600 feet from point of contact.

• The temperature of lightning's return stroke is (5) five times hotter than the surface of the sun. It can reach about 55,000 degrees Fahrenheit in contrast to about 10,000 degrees Fahrenheit for the surface of the sun. This high temperature will immediately turn water or water vapor into high pressure superheated steam. This high pressure steam can explode the clothes off your body, explode the bark from a tree, explode concrete, drywall, wood or any material containing even small amounts of moisture.

• WARNING   30 Second / 30 Minute Rule -  A popular warning method that has been widely used for many years is the "Flash-To-Bang" method that resulted in the creation of half of the 30 second /30 minute rule.  The method suggest that when you see a lightning flash, count the seconds to the bang of thunder, then divide the number of seconds by five (sound travels one mile in five seconds) to give the distance in miles from you to the lightning. For example: you hear thunder 30 seconds after you see lightning, the distance is may be 6 miles.  Thus the reason for the first number of the 30/30 rule.
  
  The accuracy of this method depends on your ability to measure the distance between a witnessed lighting strike and your observing location and is unreliable for a number of reasons. One reason is the  maximum distance you can hear thunder is as short as two (2) miles and seldom exceeds twelve (12) miles. Many factors contribute to this wide range, some of which are wind speed, wind direction, terrain, ambient noise and the origin of the return stroke. It is quite possible to have a close lightning strike and never hear any thunder, rendering this method useless.  A second reason is that lightning can travel much further than 6 miles. 
  
  Unfortunately, the "Flash-To-Bang" method this was never a good method to adequately provide a safe warning of a pending unsafe condition and should not be used today as a warning methodology.   Lightning can easily travel further than you can see. If you see lighting you are already in danger and should seek a safe location. If you hear thunder you are in immediate danger and should seek a safe location immediately.

  The second number of the 30/30 rule ask you to remain in a safe location for 30 minutes after the last sight of lightning or the sound of thunder.  This remains as good advice.  50% of the fatalities occur after the storm has passed because people resumed activities to soon after the storm.

• About 20 million cloud-to-ground lightning strikes occur annually in the USA. That's just under one per second for the USA and about 100 per second world wide

• Typically, more than 2,000 thunderstorms are active throughout the world at a given moment, producing on the order of 100 flashes per second.  

• A lightning flash is composed of a series of strokes from about 3 to 20, with an average of about four. The duration of each lightning stroke can vary, but typically average about 30 microseconds. (The average peak power per stroke is about 10¹² watts. 

• The energy contained in a single lightning stroke can power a 100 Watt light bulb for 90 days, which is equivalent to 215 kWh (kilo-Watt hours).

• About 1% of the energy in a single lightning stroke is converted to electromagnetic energy. This can be thought of as having about 200,000 clear channel 50 kW radio transmitters all turned on at the same time feeding one antenna. The wave front can propagate half way around the earth.

• U S Department of Agriculture estimates that lightning causes over 80 percent of all accidental livestock deaths.

• 31 % of beetle infestations over a three-year period were related to individual lightning-strikes of pine trees  (research done in Louisiana)

• The US averages about 100,000 thunderstorms each year (LPI)

• The danger of lightning is often under publicized and misunderstood because it usually kills people one at a time. Lightning is one of the most dangerous features of a thunderstorm.  

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During a power blackout from a lightning strike, it’s hard to remember that some good does come from the powerful bursts of electrical energy. When lightning bolts discharge, they ionize the air and produce nitrogen oxide. According to recent studies, this process could generate more than 50 percent of the usable nitrogen in the atmosphere and soil. Nitrogen is an essential plant fertilizer. Lightning also plays a critical role in the natural cycle of forests by helping generate new growth. Areas that are burned by lightning-triggered fires are cleared of dead trees so that seedlings have the space and soil to take root. The global array of thunderstorms serves as a worldwide circuit of electrical generators. Through the activity of the lightning they produce, these generators continually maintain and renew the atmosphere’s positive electrical charge.

Trivia

Thales, the Greek philosopher, in about 600 B.C., found that a piece of amber when rubbed briskly with a dry cloth would attract feathers or straw. Wm. Gilbert, the court physician to Queen Elizabeth in the 1500's, repeated this experiment and named the science of studying it vis electrica. The Greek word electra means amber. Our word for electricity is derived from this.