Lightning and lightning safety basics

The 22nd annual United States Lightning Safety Awareness Week started on Sunday, June 19, 2022, and we at Vaisala are proud to support efforts to keep people all around the world safe from lightning. Throughout this week, we will be sharing information about lightning and lightning detection to help you be more aware of this weather hazard.

Because lightning and lightning detection can be quite technical, we’ve put together this blog. Here, you’ll find some frequently asked questions about lightning and lightning detection, with lots of great information about this fascinating subject.

What is lightning?

Simply put, lightning is a giant spark in the atmosphere that occurs between the cloud and the ground (cloud-to-ground lightning) or within a single cloud, between multiple clouds, or from a cloud to the air (in-cloud lightning). About 75% of the lightning that occurs is in-cloud lightning and the other 25% is cloud-to-ground lightning. Each year, Vaisala detects more than two billion lightning events around the world.

I keep hearing words like stroke, pulse, flash, and strike. What are they?

These are all words that refer to different lightning events. 

When you look outside and see cloud-to-ground lightning flickering, that whole flickering process is what we call a cloud-to-ground lightning flash. Lightning flashes flicker because they are generally made up of multiple cloud-to-ground lightning strokes. The individual lightning strokes are detected by lightning detection networks such as the National Lightning Detection Network NLDN or Global Lightning Detection Network GLD360. Lightning strokes in the same flash can hit different points on the ground, each place it hits is a strike point, and we can identify these strike points.

In-cloud lightning flashes have large horizontal extents through clouds and individual electrical pulses through the flash are detected by lightning detection networks as in-cloud pulses.

What are some neat facts about lightning that I can use to impress my friends?

• Lightning is hotter than the surface of the sun at more than 30,000°C. This rapid heating of the air causes a shockwave that we hear as thunder.
• Lightning is only about as big around as a golf ball.
• The electrical current that runs through lightning measures from around 2,000 to more than 200,000 amperes. The electricity that runs through walls in the USA is usually around 15 amperes.
• Lightning occurs in thunderstorms, hurricanes, snowstorms, wildfires, and volcanoes.
• Lightning has been detected within 52 kilometers of the North Pole.

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How is lightning detected?

Every time lightning occurs, it produces electromagnetic waves that travel around the world at the speed of light. Vaisala has installed ground-based sensors around the United States (NLDN) and around the world (GLD360) that “listen” for the lightning waves. When the lightning waves reach each sensor, the time that it arrived and the direction it came from are recorded. When multiple sensors detect the same lightning wave, our systems calculate the location and the time the lightning occurred. Lightning data in the United States is calculated as fast as 11 seconds from the time the lightning occurred. Global lightning data is calculated around 30 seconds from the time the lightning occurred. Vaisala’s networks have been designed to give the highest quality detection performance anywhere in the world.

11 seconds sounds fast, but can you tell us when and where lightning will happen? Can you predict lightning?

Scientists are still working to understand how lightning occurs and why some storms will produce more lightning than other storms in the same environment. The time and location of any lightning flash cannot be predicted. Sensors that measure the electric field or electrostatics in the atmosphere can detect the presence of electrical charge but cannot be used to say that lightning will occur in the area. These systems can over-warn for the potential for lightning or even fail to warn for lightning. Lightning detection data is the best way to be aware of thunderstorms moving towards your location.

When lightning has been detected nearby, what should I do?

The lightning safety adage is “When thunder roars, go indoors!” The safest place to be during a thunderstorm is in a sturdy structure like a house, store, or other building that has electrical wiring and plumbing running through the walls. If you aren’t near a safe structure like that, a fully enclosed metal vehicle is another safe place to be. 

Oh yeah, I’ve always heard cars are safe because of the tires.

This is a myth. Cars are safe during thunderstorms because if lightning were to strike a car, the electricity would run through the metal shell of the car and not impact its occupants. Along those same lines, rubber shoes do not protect you from lightning either.

This is all great information, what more can you tell me?

We’ll have a lot more information about lightning and lightning safety this week on our blog and social media accounts. Be sure to check the other blogs that we’ve posted about lightning on Lightning fast facts.