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Lightning, which occurs during all thunderstorms, is the result of a buildup and discharge of electrical energy between positively and negatively charged areas. Each lightning stroke can carry up to 100 million volts of electricity and leap from cloud to cloud or cloud to ground and vice versa. Lightning tends to strike higher ground and prominent objects, especially good conductors of electricity such as metal.

These huge electrical sparks are one of the leading causes of weather related deaths in North America. Although the chances of being struck by lightning are estimated to be 1 in 700,000, 73 people are killed and 300 are injured every year, on average. The people who do survive a lightning strike often report a variety of long-term debilitating symptoms including memory loss, attention deficits, sleep disorders, numbness, dizziness, and an inability to sit for long periods of time.

Thunder is the noise caused by the explosive expansion of air due to the heat generated by the lightning discharge. Thunder may have a sharp cracking sound when lightning is close by, compared to rumbling noise produced by more distant strokes. Because light travels at a faster speed than sound, you can see a lightning bolt before the sound of thunder reaches you.

To judge how close lightning is, count the seconds between the flash and the thunder clap. Each second represents about 300 meters. If you can count less than 30 seconds between the lightning strike and the thunder, this means that the storm is less than 10 Km away. There is an 80% chance that the next strike will happen within that 10 Km.

Lightning may strike several kilometres away from the parent cloud. Precautions should be taken even if the thunderstorm is not directly overhead. 

THE 30 – 30 RULE

Take appropriate shelter when you can count 30 seconds or less between lightning and thunder. You should remain in the sheltered area for 30 minutes after the last thunder. 


  • Keep a safe distance from tall objects such as trees, hilltops, and utility poles.
  • If you are in a forest, seek shelter in a low area under a thick growth of small trees.
  • If in an open field, avoid projecting above the surrounding landscape by seeking shelter in low-lying areas such as valleys, ditches and depressions. Crouch down, put feet together and place hands over ears. Be alert for flash floods.
  • Avoid isolated sheds or other small structures in open areas.
  • Stay away from anything metal: industrial/farm equipment, golf clubs, bicycles, open air motorized vehicles such as convertibles motorcycles, golf carts, ATV’s, wire fences, clotheslines, metal pipes, rails, and other metallic paths that could carry lightning to you from some distance away.
  • Feeling your hair stand on end is an indicator that lightning is about to strike. You must try to make yourself the smallest target possible and minimize your contact with the ground. Squat low to the ground on the balls of your feet. Place your hands over your ears and put your head between your knees. DO NOT lie flat on the ground.
  • Keep a minimum distance of five meters from other people.
  • Stay away from water. DO NOT go boating or swimming if a storm threatens. 


  • Stay away from doors and windows.
  • DO NOT use a corded telephone, except in an emergency. Cordless and cellular telephones are safer to use.
  • Take off headsets.
  • Turn off, unplug, and stay away from appliances, computers, power tools, and televisions. Power surges from lightning can cause serious damage.
  • Avoid showering or bathing. Plumbing and bathroom fixtures can conduct electricity. 


  • Keep a watchful eye to changes in the weather.
  • Carry a portable weather radio.
  • If a thunderstorm watch/warning has been issued, consider postponing any outdoor activities.
  • Remember the 30 – 30 lightning safety rule: go indoors if, after seeing lightning, you cannot count to 30 before hearing thunder. Stay indoors for 30 minutes after the last clap of thunder.
  • Rubber soled shoes and rubber tires provide NO protection from lightning. The steel frame of a hard topped vehicle does provide increased protection if you are not touching metal. Although you may be injured if lightning strikes your car, you are much safer inside a vehicle than outside.

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