How To Calculate the Distance from Lightning

Thunder and lightning are fascinating phenomena, from time immemorial to the time Benjamin Franklin decided to conduct his experiments with a kite. Elementary studies let us know that light and sound travel through air or other media at different speeds, which is why you often hear the sound of thunder after you actually see the lightning. Lightning occurs on account of the creation and discharge of electrical energy between areas of opposite conductance. This can happen between clouds, within a cloud or from the cloud to the ground. Rapid heating and cooling of air during lightning cause shock waves which we hear as thunder.

How does one find out where exactly lightning is striking? How near or far from you is this happening? If you're interested in knowing, then read on...


  1. Check the sky for the next immediate flash of lightning.
  2. Count the number of seconds from the time you see the flash till you hear the sound of thunder.
  3. Divide the total seconds counted as above by 5. The answer is the distance in miles of how far away the lightning is from you.

    For example, if you counted a total of 10 seconds between the first flash till the time you heard the thunder, the lightning strike is 2 miles away from you. To calculate in kilometers, 1 mile= 1.609 kilometers, hence the distance will be approximately 3.22 kilometers.


  • Light and sound travel at different speeds, the former much faster than the latter.
  • The speed of sound is affected by the media in which it travels - vacuum, air, etc. In air, factors such as humidity, temperature, height and density determine the speed at which sound will travel.
  • Lightning does not occur as a single strike; often there will be several simultaneous flashes and it may become difficult to trace which flash caused the exact sounds you will be hearing.
  • This is just a simple approximate method to calculate the distance, not 100% foolproof. Lightning can spread over a radius of up to 10-15 miles for a single flash, so a safe distance to be away from being hit by lightning should be a minimum of the above distance range or more.
  • It is best to take to the nearest shelter which is fully covered. Do not be in contact with any metal object or surface since most metals are good conductors of electricity and lightning is an electrical charge!!

It is very important to remember that lightning can kill and your first basic reaction should be to find safe shelter. "Forewarned is forearmed" and hence, keep track of the latest weather updates before heading out; seek a safe shelter immediately should you be caught outdoors; and stay away from tall isolated objects such as trees, towers or poles. Immediate CPR and first aid for affected persons is recommended.


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