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Lightning Safety Program
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Understanding Lightning

Lightning is fascinating to watch but also extremely dangerous. In the United States, there are an estimated 25 million lightning flashes in a typical year. Each of those 25 million flashes is potential killer. While lightning fatalities have decreased over the past 30 years, lightning continues to be one of the greatest storm-related killers in the United States. In addition, lightning injures many more people than it kills and leaves some victims with life-long neurological problems.

lightning strike map

Understanding the science of lightning is just the first step in understanding why it is so important to get to a safe place anytime thunderstorms are in the area. If you can hear thunder–even a distant rumble or a crackling aloft–you are already in danger of becoming a lightning victim. Immediate actions and proper planning can greatly reduce your chances of becoming a lightning victim.

With rare exception (such as volcanic eruptions and large forest fires), virtually all lightning is produced by thunderstorms. In simple terms, lightning is a giant spark of electricity in the atmosphere or between the atmosphere and the ground. As lightning passes through air, it can heat the air to 50,000 degrees Fahrenheit (about 5 times hotter than the surface of the sun).

The process begins with the development of a thunderstorm. As a thunderstorm develops, charges build up in the thunderstorm cloud and on the ground under and near the thunderstorm. Normally, air is poor conductor of electricity and prevents the movement of electrical charges. However, when the charge differences in the cloud or between the cloud and the ground become too great, a sudden, violent, and potentially deadly discharge occurs. We call this discharge “lightning.”

Lightning can be divided into several types. The two main types are intra-cloud lightning and cloud-to-ground lightning. Intra-cloud lightning is simply an electrical discharge between oppositely charged areas within the thunderstorm cloud. Cloud-to-ground lightning is an electrical discharge between opposite charges in the cloud and on the ground. For people on the ground, cloud-to-ground lightning is the greatest concern.

Learn More: Thunderstorm Development

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