Understanding Lightning

There are about 100 deaths from lightning every year in the United States. Some may say that's a small number, until they consider that some 1000 more people will be injured or permanently disabled from a lightning strike. Unfortunately, many people still believe that being struck by lightning is an improbable event. This is not so. There is a probability that 1 in 300 Americans will be affected by a lightning strike during their life.

So what exactly is lightning? Lightning can be described as a sudden, brief, and brilliant flash or light, often accompanied by thunder, produced by electrical discharges within and near cumulonimbus clouds.

Lightning, simply put, is a giant electric discharge. Its nature's way of equalizing opposing electrical charges. I'm sure we've all experienced small static shocks when reaching for a door knob or some other metal object. Well, the principles of lightning are basically the same. Wind and water particles (or ice particles) create an electric charge in the cloud (usually a positive charge at the top of the cloud and negative at the bottom). The cloud's intense negative charge (focused at the bottom) induces a positive charge on the ground below. When the difference of charge becomes great enough, the air breaks down and forms a path for the electric discharge. Lightning is then seen arching between the cloud and ground. Cloud-to-cloud lightning can also occur when this difference of charge is great enough within the cloud itself.

Some quick facts about lightning:

  • - Lightning (and the air around it) easily reaches 20,000°F (11,000°C), which is hotter than the surface of the sun.
  • - The rapid expansion of the heated air around a lightning bolt is heard as thunder.
  • - Thunder can usually be heard up to 8 or 10 miles (about 13 - 16 km).
  • - You can estimate the distance of a lightning bolt by counting the seconds between seeing the flash of light and hearing its thunder. Every 5 seconds equals 1 mile.
  • - It is usually safe to resume outdoor activities if you have not heard any thunder for 30 minutes.

Lightning Safety

a lightning-damaged tree

There are several things you can do to decrease the likely hood that you will be struck by lightning. Use the following information to help stay safe during lightning storms.

When Indoors

Stay away from windows and doors and keep them closed. Avoid using underground plumbing (ex. tap water). Do not use a wired telephone and disconnect electrical appliances. Do not go back outside unless absolutely necessary.

When Outdoors

Seek a proper shelter immediately. If you can't reach shelter, stay away from tall objects such as trees and towers. Stay clear of high ground and open fields. Move towards low-lying areas such as valleys, ditches and depressions, but be aware of the risk of flash floods. If you're caught in a level field, crouch down into a ball and use your hands to protect your hearing. Never lie down flat on the ground. If you are in a group, spread out, keeping at least 15 feet apart.

In a Vehicle

Lightning moves over the outer surface of metal objects, so you will be safe inside an all-metal vehicle. Avoid touching anything metal inside and keep your hands in your lap. Avoid parking near trees or power lines as they may fall during a storm. If a power line falls on or near your vehicle, don't step outside. Convertibles are not safe because the outer body (the car's chassis) is what that offers protection and not the rubber tires. Remember, a few inches of rubber is not going to stop a bolt of lightning that just traveled thousands of feet through the air.