IN-DEPTH ANALYSIS: Lightning — 30,000 °C and 5 times hotter than the Sun’s surface

Maxime Marquette

2026-06-24 13:09:54

The Formation of Electric Charge in Cumulonimbus Clouds

It all begins in cumulonimbus clouds—those immense storm clouds that can rise to altitudes of 15 to 20 kilometers. Inside these clouds, ice crystals and hailstones are swept up and down by violent updrafts and downdrafts. These collisions between ice particles generate transfers of electrical charge: small, light crystals tend to become positively charged and rise with the warm currents, while heavier particles (hailstones, graupel) become negatively charged and fall.

This phenomenon—known to specialists as the non-inductive process—creates a massive separation of charges: the base of the cloud becomes strongly negative, and the ground below, under the influence of this charge, becomes positively charged by induction. The voltage that builds up between the base of the cloud and the ground can reach staggering levels: from 100 million to 1 billion volts.

The Return Path: The Formation of the Plasma Channel

When the electrical voltage exceeds the dielectric strength of the air, a discharge begins. Initially invisible, a “downleader” advances in 50- to 100-meter jumps from the base of the cloud toward the ground. At the same time, “upward tracers” rise from the ground, particularly from elevated points (trees, church steeples, lightning rods). When the two meet, the circuit closes and the current surges through: this is the “lightning return stroke,” the main discharge that we see.

This return stroke travels at speeds of up to 200 to 300 million meters per second—a substantial fraction of the speed of light. It is this lightning-fast reverse current that heats the air channel to 30,000 °C in a few millionths of a second. The air literally doesn’t have time to expand normally—it is propelled into a supersonic shock wave that we hear as thunder.

There is something almost poetic about the fact that what we perceive as the deep, frightening sound of thunder is actually the sound of a shock wave generated by a stream of air heated to 30,000 degrees—hotter than the surface of a star. Nature does some mind-blowing things on a shoestring budget.

Lightning plasma: the fourth state of matter

When Air Becomes Plasma

At 30,000 °C, air no longer behaves like an ordinary gas. It enters the fourth state of matter: plasma. In this state, nitrogen and oxygen molecules are so violently agitated that they break apart and become ionized—their electrons are stripped away, leaving positively charged ions in a cloud of free electrons. This ionized mixture conducts electricity and emits a blinding white light visible from tens of kilometers away.

This plasma channel is extraordinarily narrow: its average diameter is about 3 to 5 centimeters. Yes—that glow you see streaking across the sky, that luminous line that can be 5 to 25 kilometers long, is actually nothing more than a tube of plasma barely thicker than a bottle. All the storm’s energy is concentrated in this nearly invisible filament—and it is this concentration that produces the extreme temperatures.

Energy and Duration: A Brief but Colossal Flash of Lightning

The total duration of a lightning strike is about a quarter of a second, but the main lightning return lasts only a few thousandths of a second. In that tiny fraction of a second, an average lightning strike releases about 250 kilowatt-hours of energy—enough to power a 100-watt light bulb for more than three months. The current in a lightning strike can reach 200,000 amperes—tens of thousands of times the current of a standard household outlet.

However, the total energy of a thunderstorm remains difficult to harness industrially: the discharge is too brief, too unpredictable, and too unstructured to be captured and stored in an economically viable way with current technologies. Lightning is a phenomenon of incredible instantaneous power but modest total energy compared to the needs of an electrical grid.

People sometimes dream of harnessing lightning as an energy source. Unfortunately, the physics of the problem are unforgiving: all that power concentrated in a quarter of a second is impressive, but it’s exactly the kind of engineering problem that makes you want to cry into your coffee.

Types of Lightning and Associated Phenomena

Intracloud, intercloud, and ground lightning

Contrary to popular belief, most lightning strikes do not reach the ground. According to NOAA data, intracloud lightning (within the same cloud) accounts for about 75% of all lightning strikes, intercloud lightning for about 5 to 10%, and cloud-to-ground lightning—the most dangerous and spectacular—for about 20%. In the United States alone, the National Lightning Detection Network (NLDN) records an average of 20 million cloud-to-ground lightning strikes per year across the 48 contiguous states.

There are also rare atmospheric light phenomena associated with thunderstorms: sprites (red glows above thunderclouds), blue jets, and elves (luminous rings at very high altitudes). These phenomena, observed since the 1990s and now well documented by the International Space Station, demonstrate the electrical complexity of Earth’s atmosphere, which we are only beginning to understand.

Global Lightning: A Constant Phenomenon

At this very moment—as you read these lines—about 100 lightning strikes occur every second across the entire planet Earth. This is known as permanent global lightning activity. The Earth constantly maintains a global atmospheric electrical circuit: thunderstorms positively charge the ionosphere and negatively charge the ground, and this imbalance is partially resolved by fair-weather currents. Lightning is not an atmospheric anomaly—it is a fundamental component of the Earth’s electrical circuit.

100 flashes of lightning per second. I find this figure both reassuring and mind-boggling. The planet “humms” electrically around the clock, and we go about our lives deep within this electric ocean without ever giving it a thought. Until a thunderstorm strikes.

Dangers, Protections, and Myths

What Lightning Can Do to Materials and Living Things

At 30,000 °C, lightning can instantly vaporize the water contained in trees, causing them to literally explode under the effect of vapor pressure. It can melt metal parts, vitrify sand into fulgurites (those tubes of molten-solidified sand sometimes found in deserts), and cause fires at considerable distances. The effects on the human body when struck by lightning are complex: the majority of victims (about 90% in France) survive, but often suffer lasting neurological damage related to the current passing through the nervous system.

The lightning rod, invented by Benjamin Franklin in 1752, remains the most effective protective device: it provides the current with a preferred conductive path to the ground, preventing the lightning from seeking its own path through less conductive structures. This basic principle—providing a path of least resistance—has remained unchanged since Franklin’s time, even though modern protection systems are far more sophisticated.

Myths to Debunk

Several misconceptions persist about lightning. “Lightning never strikes the same place twice” is a complete myth: the Empire State Building in New York is struck an average of 20 to 25 times a year. “Cars are protected because of their rubber tires” is also false: it is the Faraday cage formed by the metal body that protects the occupants, not the tires. And “lying flat on your stomach during a thunderstorm” is not recommended: the best protective position is to crouch on the balls of your feet, with your feet together, to minimize the contact area with the conductive ground.

The myth that “lightning never strikes the same place twice” has likely cost lives. It’s the perfect example of how a poetic metaphor can become dangerous when mistaken for a scientific fact. Lightning rods work precisely because lightning LOVES to strike the same place.

Conclusion: Lightning, That Marvel of the Atmosphere

Extreme Physics in Our Daily Lives

Lightning is one of those natural phenomena that, all on its own, encapsulates the full power and elegance of physics. In a fraction of a second, it mobilizes millions of volts and hundreds of thousands of amperes, reaches temperatures that exceed those on the Sun’s surface, creates plasma, generates supersonic shock waves, and recharges the planet’s global electrical circuit. All of this within a filament just 3 centimeters in diameter.

The next time a thunderstorm rumbles overhead, take a moment—from the safety of shelter, of course—to appreciate the spectacle. You’re watching stellar physics unfold in your atmosphere. Not bad for a phenomenon that humans have tried to explain as the wrath of the gods for millennia.

The Research Continues

Lightning has not yet revealed all its secrets. The exact formation of electrical charges in cumulonimbus clouds is not yet fully understood. Transient luminous phenomena such as sprites and blue jets continue to be actively studied. The role of lightning in atmospheric chemistry—particularly the production of nitrogen compounds that act as fertilizers—remains an active area of research. From Benjamin Franklin to the International Space Station, lightning remains an inexhaustible source of discoveries.

By Maxime Marquette, columnist