University of Vermont Extension 
Department of Plant and Soil Science

Summer News Article

Dr. Leonard Perry, Extension Professor
University of Vermont
As much as you may want to remain outside gardening with thunderstorms in the distance, don’t!  Thunderstorms often mean lightning, and lightning can kill.  There are some important facts to know about lightning if you work outside in order to remain safe.

There are about 25 million lightning flashes in a year.  About 66 people are killed in an average year from lightning, about the same as killed from tornadoes.  Yet without the mass destruction and killings of tornadoes, lighting often is not taken seriously.  Lightning can injure or kill in three main ways—from a direct hit, from “step voltage” radiating through the ground from a hit tree or pole, or from fires or fallen trees as a result of a lightning hit.

Thunderstorms produce lightning, as well as the thunder you hear.  Even if you don’t see a thunderstorm, perhaps over the horizon or a hill, if you hear one there is a good chance there may be lightning.  You can hear thunder about 10 miles away, which is how far away lightning can strike as well.  Successive lighting strikes often are within three miles, so if you see lighting this close take shelter immediately.

To tell how far away the lightning is, count the number of seconds between when you first see the lightning, and first hear the thunder.  Then divide by five.  So, if the elapsed time is 15 seconds, the lightning is about 3 miles away.  This formula comes from the fact that light travels faster than sound, in fact about one mile in five seconds.  In this example, you saw the
lightning almost instantly, yet it took 15 seconds for the thunder sound to reach you from when it and the lightning took place.

Here are some tips to follow during thunderstorms and lightning if you are gardening.

*At the first sound of thunder or notice of lightning, go indoors.  If you’re in the middle of a project, and the lightning is close, leave immediately.  You can pick up later.  Stay indoors for about 30 minutes after the last observed lightning and thunder.  Consider this a good time to take a break, even read a garden magazine or book!  But don’t go on the computer or telephone as these can conduct a lightning strike to you.  Best is to unplug electronics and appliances.  Keep away from windows, tempting as the storm might be to watch.  Don’t use this as the time to take a bath or shower either.
*If you are caught outside away from buildings, seek shelter in a car, or low area such as a ditch.  AVOID water, high ground, open spaces, metal objects such as tools, being on tractors and machinery, canopies, small rain shelters, or trees. 
*If you are caught unaware, and lightning strikes nearby, crouch down but do not lie down.  Put your feet together.  Place hands over your ears to minimize any hearing damage.  Keep at least 15 feet away from other people. 

If a person is injured by lightning, directly or indirectly, get to them and call 911 immediately.  Make sure any victim has a medical examination, as damage may not be apparent.  More tips on lightning safety, and helping victims, can be found in a bulletin from University of Maine Extension, or from the National Weather Service (


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