Weather Forecast


Wheeler: What happens when lightning strikes

Any square mile of land in the Fargo-Moorhead area will receive an average of about five lightning strikes per year.

A particularly vivid lightning storm passing over the area might make this number seem too low. However, most lightning does not strike the ground but remains within the cloud. In-cloud lightning is the result of charge separation within the cloud itself.

The very dynamic air currents in a thunderstorm will spread charge throughout the cloud, causing lightning. When thunderstorms happen at night, it is easier to see all the vivid in-cloud lightning illuminating the cloud and reflecting all across the sky.

When lightning does connect with the ground, it usually does so through tall objects, as these provide a better path than the air for the current to flow. The vast majority of the lightning strikes in the Fargo-Moorhead area are through communications towers and tall buildings that are designed to let that current connect to the ground without causing damage.

Still, several times each summer, lightning does manage to strike a few trees, houses and other buildings in and around the city, and the result is usually not good. Lightning in a house will find the most efficient way to ground itself, and that usually means the electricity will travel through metal cables or pipes. These are not designed to carry such extreme current and are often overheated to the point of starting a fire.

Televisions and computers do not fare well in a lightning strike and are usually damaged beyond repair. Contemporary plastic plumbing connections do not carry any electrical charge in a lightning strike, but copper plumbing in older construction does and this can make sinks, showers and bathtubs very unsafe places to be during a thunderstorm.

If you are lucky, some of the current in a lightning strike will pass around the shell of the building. If it is raining, much of the current can be dispersed to the ground by the water, which is actually a pretty good electrical conductor. Steel siding can also provide a way for the current to pass around, rather than through, a house.

When lightning strikes a tree, moisture and sap is instantly vaporized, causing parts of the tree to explode.

And that old adage about a car being a safe place to be in a thunderstorm may be losing some of its truth. Rubber tires do not protect people in a car from lightning. If your car is struck, consider that the lightning has already passed through thousands of feet of air to get to your car. A half-inch of steel-belted, synthetic rubber is not going to stop it.

Lightning tends to pass around the metal shell of the car, leaving the passengers safe inside. But as car bodies are made of less steel and more plastic, this might not work as well. So if your car is hit by lightning, you should hope it is raining hard enough for the plastic exterior to be wet enough to carry the charge.

John Wheeler is chief meteorologist at WDAY