What is Thunder, and Where Does It Come From? Can Thunder Exist Without Lightning? Which Comes First – Thunder or Lightning? Where is Earth’s Thunderstorm Center? Plus: The Dangers of Loud Thunder and How It Differs From a Storm
We explain this natural phenomenon in the simplest terms.
What is Thunder, and How Does It Form?
Thunder is an atmospheric acoustic phenomenon that occurs during thunderstorms and accompanies lightning discharges.
Lightning, in turn, is an electrical discharge that occurs when air inside a cloud heats up, or between cloud layers, or between clouds and the ground. This causes rapid expansion and compression of air bubbles, first creating lightning (essentially an explosion) followed by loud rumbling.
Thunder occurs when lightning heats the air to about 30,000 °C (54,000 °F), causing it to expand rapidly and create a shock wave. Essentially, at the moment of the lightning discharge, areas of high and low pressure form and collide violently, producing a loud explosion.
How Thunder Differs From a Thunderstorm
The difference between thunder and a thunderstorm lies in the definitions themselves. Thunder is simply the sound of colliding electrical discharges in the atmosphere. A thunderstorm is a weather phenomenon that combines several elements: the formation of thunderclouds, lightning discharges, isolated thunder or rolling thunderclaps, and precipitation. Thunder can occur without rain.
The closer the storm, the more intense the lightning and the louder the thunder.
Why Does Thunder Rumble?
How does thunder form? The lightning discharge itself doesn’t happen instantaneously – it takes some time. The rumbling results from refraction (bending) of sound waves as they distort depending on the lightning channel’s curvature.
The longer the lightning bolt, the more rumbling thunder will occur.
Thunder can typically be heard at great distances from the lightning strike location – up to 15 kilometers (9 miles) in noisy urban areas and up to 25 kilometers (15.5 miles) on quiet nights in rural forested areas.
Which Comes First – Thunder or Lightning?
Thunder is essentially the shock wave from lightning transformed into a sound wave. Therefore, it cannot exist without an electrical discharge.
So there should be no thunder without lightning. But can there be lightning without thunder? Yes – when lightning is very far away. It might seem like there’s no thunder. In reality, we just can’t hear it. This happens rarely and most often in summer. Flashes of distant lightning in completely clear skies are sometimes called heat lightning or “star lightning.” High-altitude translucent clouds composed of small ice crystals (once poetically called “serpentine clouds”) can amplify the light wave.
In exceptional cases, lightning isn’t accompanied by thunder if the discharge strikes underwater. Interestingly, what we usually see is actually the return stroke of the lightning – the so-called streamer ribbon emission reflected from the ground back into the sky, as it’s typically much stronger and brighter than the primary, literal lightning-fast discharge from sky to ground.
Now let’s recall physics from school. The speed of light is nearly a million times faster than the speed of sound. This is why there’s a convenient way to estimate a storm’s distance. The speed of sound in atmospheric temperatures ranging from -50 °C to +50 °C (-58 °F to 122 °F) is approximately 300–360 meters per second (980-1,180 feet per second). By multiplying this value by the time between thunder and lightning flash, you can determine how far away the storm is. Three seconds correspond to about one kilometer (0.62 miles).
Why Thunder Sometimes Occurs Without Visible Lightning
The expression “like thunder out of a clear blue sky” isn’t just a figure of speech meaning surprise – it’s also an interesting natural phenomenon. Most likely, it has nothing to do with thunderstorms. In one region of India, repeated “thunder” sounds without any visible storm or clouds periodically frighten local residents. This occurs in the same location over the Ganges River delta, most often in morning hours. The phenomenon even has its own name – Barisal Guns. Also called mistpoeffers or airquakes. Similar occurrences have been observed over the Connecticut River and in New York State over Seneca Lake.
Scientists have proposed numerous theories about this thunder without lightning – from unusual atmospheric electrical discharges to underground tremors. But so far, no definitive explanation for this unusual phenomenon has been found.
How Dangerous Is Loud Thunder?
Thunderstorms are dangerous weather events. In terms of human casualties and property damage, they’re second only to floods. Storms approach rapidly. Typically, thunderclouds move at 5-8 m/s (20-30 km/h or 12-18 mph). By assessing wind direction, you can roughly estimate whether the storm will reach you before you can find shelter.
However, thunder itself poses no direct threat to humans or structures. The loudness of thunderclaps can reach 120 decibels, but by the time the sound reaches human ears, its intensity decreases significantly and can’t harm hearing.
Potential Effects of Extremely Loud Thunder
- Temporary ear ringing or muffled hearing that fades with time
- In anxious individuals – nervous breakdowns, tics, or epileptic episodes
- In children – stuttering from severe fright caused by the loud noise
