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Thunderstorms are a constant part of summer in the Lower 48, and they all produce lightning, a wild phenomenon that can also be dangerous. In D.C. on Thursday, two people died after being hospitalized with injuries sustained in an apparent lightning strike near the White House.
These bolts of raw electricity ricochet through thin air, arcing from the stormy skies and blasting anything they hit with a deafening roar. Lightning can be mesmerizing, dangerous, beautiful and terrifying, but how much do you know what happens when it strikes?
Two people died after being struck by lightning Thursday night near the White House
Lightning is an electrical discharge and nature’s balancing mechanism for distributing charge in the atmosphere.
Thunderstorms become electrified when electrons, which are negatively charged particles, are shed from one water particle—such as a raindrop, snowflake, or hailstone—and land on another, leaving the former with a net positive charge and the latter slightly more negative. Generally speaking, ice crystals acquire a positive charge, while raindrops acquire a negative charge.
This makes the top of the cloud, where the temperature is well below freezing, positively charged. Below that is a more extensive “central negative” within the storm. A shallow, broad positive charge sits at the base of the storm like the bottom of a hamburger bun.
Most of the lightning we see is either intracloud (in the cloud) or takes the form of cloud-to-ground lightning, most commonly originating from from the average negative charge. The greater the electric field in the cloud, the more sparkly the storm will be.
Getting an electric spark to jump through the air is difficult. The surrounding electric field must be large enough to overcome the “dielectric breakdown strength” of air.
Consider a dam. It prevents water from flowing beyond it unless the volume of water behind it reaches a threshold sufficient to burst the dam. Then the accumulated water can break through unhindered.
For air, this magic number is 3 megavolts (or 3 million volts) per meter for dry air (it will change a bit in a storm). The charge building up on the surface will begin to leak into the air in a fine stream of electrons known as a “corona” discharge. This heats up the surrounding air, reduces resistance and makes it possible for that spark to start spreading in jagged steps.
It’s unclear what processes unfold in the cloud, but eventually what’s called a “step leader” of electricity races toward the ground, leaping in a branching, fractal pattern.
What I learned from 20 years of shooting lightning in Washington
“Upward spiraling jets,” or narrow streaks of electricity, extend skyward from the surface, like a group of students raising their hands. Eventually, the downward stepped conductor connects to one of the upward streamers to create a continuous channel of electricity between the cloud and the ground. Current pulses pass through the channel, each one causing a burst of light. That’s why lightning seems to flicker.
Surprising facts about lightning
- The flash is not that dense. It’s actually only an inch or two in diameter. It just looks wider because of the lighting.
- Lightning is five times hotter than the surface of the sun. In this narrow lightning channel, electricity heats the air to almost 55,000 degrees. This causes the air to expand rapidly, which creates the atmospheric shock wave we hear as thunder.
- The flash can be fired. Researchers at Los Alamos National Laboratory in New Mexico use rockets to trigger lightning, then use high-speed cameras and instruments to collect data. It’s also well established that airplanes, helicopters, tall man-made structures, and even wind turbines can cause shocks of their own.
- “Rising Lightning” is a thing. It’s exactly what it sounds like – lightning that jumps from the ground to the cloud, spreading outward along the expansive lower positive charge of the cloud. Indeed, self-initiated ascending leaders are common from man-made transmission/broadcast towers and are an emerging area of research.
- Some lightning strikes are more likely to start wildfires. Although the flash is extremely hot, it is also short. This limits his window of opportunity to start a forest fire. But instead of current flowing between heaven and earth in a short series of staccato bursts, some lightning takes the form of a “continuous current” discharge. This means that the current flows in pulses of longer duration. As the current heats the ground for a longer time, the chances of a forest fire increase significantly.
- Men are hit approximately four times more often than women. In the United States, men account for 84 percent of lightning deaths, and women make up the remaining 16 percent.
- Deaths from lightning are decreasing. Due to improved forecasting, education and awareness, lightning deaths have decreased significantly in recent decades. An average of 43 people died from lightning each year in the United States between 1989 and 2018, but the average number dropped to 23 between 2012 and 2022. A record low of 11 deaths occurred in 2021.
Tips and facts you need to know to stay safe when lightning strikes
- Never take shelter under a tree. If lightning strikes a tree, the charge may pass through the trunk and laterally strike individuals below, or also spread through the ground. Many lightning tragedies stem from people seeking shelter under trees. The previous DC lightning fatality, which occurred on May 17, 1991, occurred when a group took cover under a tree during a lacrosse game.
- Recreational activities – especially fishing and boating – are the biggest sources of lightning deaths. “[F]fishermen and boaters are likely to be outdoors and more vulnerable to a direct lightning strike,” the National Lightning Safety Council said in a 2020 report.
- Lightning can strike even in blizzards. Thunderstorms are real and can be dangerous. On January 25, 1990, lightning struck a light pole during a thunderstorm in Crystal Lake, Illinois. The charge went through the frozen ground and injured 11 people nearby who were shoveling snow or hitting stranded motorists.
- Lightning can travel 10 or more miles from the main thunderstorm and even hit in the fresh air, away from any rain. These “thunderbolts” are often more powerful and powerful because they originate from the positively charged upper part of a thunderstorm. They are among the most dangerous as they can strike in otherwise calm conditions. That’s why experts recommend taking cover at the first sign of thunder, as that’s a sign you’re close enough to be struck by lightning.
- Ninety percent of lightning victims survive. There are an average of 30 lightning-related deaths in the United States each year. The lightning strike near the White House on Thursday brought the death toll this year to 11.
Read more about lightning…
“Giant jet” lightning is a mystery. These researchers are solving it.
Jonathan’s story: After the tragic ‘bolt from the blue’, two simple rules that could save your life
Clear Sky Thunder: This is how lightning can strike when the storm is tens of miles away
Where lightning strikes the most in the US in 2021
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