I recently found myself in the middle of an intense thunderstorm. While safe inside a friend’s house, the booming sounds of thunder were like nothing I had ever heard. Each explosion was stronger than the last and the walls of the house shook violently. As I helplessly watched my friend’s beagle-chihuahua run to his safe spot under the couch, I couldn’t help but wonder: Why is thunder so deafening?

To learn more about the deafening phenomenon of storms in nature and why some thunder is louder than others, popular science turned to Jonathan Belles, senior digital meteorologist at Weather.com. Their answers may surprise you!

What is thunder?

Thunder is the acoustic byproduct of lightning. To understand one, we first have to know the other.

Lightning is a massive discharge of electricity through the atmosphere; basically, a huge spark of static charge. “The rays are five times hotter than the surface of the Sun,” says Belles. It is one of the hottest natural phenomena on Earth, reaching temperatures of up to 54,000 degrees Fahrenheit.

According to Belles, “that [heat] creates a tremendous amount of energy,” causing the surrounding air to expand explosively before it rapidly cools and the surrounding air rushes back in. The result of that rapid expansion and collapse is thunder, the audible shock wave that comes from a lightning strike.

“Think about when you’re baking something in the oven,” like a loaf of bread or puff pastry, Belles says. “It will expand rapidly due to the heat of the oven.” However, if you open the oven too early, your puff pastry will fall apart. This is because any air introduced destroys the pressure necessary for the dough to hold its shape. “Lightning does something similar,” he says.

The extreme temperature of a single lightning bolt forces the air around it to expand explosively. As the beam fades, that same superheated air rapidly cools, causing air to return and fill the resulting void. That’s thunder, says Belles. It’s “the atmosphere trying to get back to where it was.”

Why are some thunders louder than others?

The sound and intensity of thunder can depend on several factors. “The terrain is one thing,” Belles says. For example, think about how a voice resonates when you are in a cave or canyon, bouncing off hard rock walls. If there is thunder in a valley, it can behave in the same way. The steep topography of the valley acts as an acoustic funnel, collecting sound waves over a large area and concentrating them to a smaller, directed point.

“If there is a mountain or reflective surface on the other end, the thunder echoes can come and go for a while.” This creates what is known as “rolling thunder,” a continuous low-frequency boom that often lasts for a few seconds.

Temperature can also play a role in thunder amplification, especially during an atmospheric (or temperature) inversion. This is a weather phenomenon in which a layer of warmer air sits on top of a layer of colder, denser air and traps that colder air close to the ground.

“It’s like creating an artificial barrier over your head,” Belles says. The warm layer also traps sound waves, causing them to bounce repeatedly between the ground and the warm layer, producing a megaphone-like effect.

During an atmospheric inversion, Belles says, thunder bounces up and down in the cold, dense air until it disperses. Think of it like setting off fireworks inside a long, narrow hallway (which, by the way, is a very bad idea). The sound is trapped and amplified.

How far away can you hear thunder?

Thunder is usually audible from 10 to 15 miles away, Belles says. However, it is possible to hear it up to 40 kilometers away under ideal atmospheric conditions, such as in a flat, calm or temperature-inverted environment.

Lightning, on the other hand, typically travels visually three or four times farther than the sound of thunder. Lightning can sometimes be seen from more than 100 miles away at night, and the flash reaches your eyes in a fraction of a second.

In contrast, thunder sound waves lose their energy much more quickly, causing them to die out faster the further they travel.

You can’t have thunder without lightning, Belles points out. “If you hear thunder but don’t see lightning, there’s usually something blocking your view.” Maybe it’s thick clouds or even the curvature of the earth.

“Summer is the best time for ‘heat lightning,’ which is a nickname for the weak lightning bolts that can appear along the horizon on warm, humid nights. “It’s not any kind of amazing phenomenon. It’s just that the lightning is far enough away that you can’t hear the thunder.”

thunder sounds

Thunder is a continuous low-frequency boom that often lasts for a few seconds. Video: Sounds of thunder, @thesoundsguy1602

What are the different types of thunder?

“There aren’t actually different types of thunder,” Belles says, “but there are many different types of lightning,” which can affect the way thunder sounds.

For example, “there is something called positive rays.” These lightning bolts originate in the upper regions of a thundercloud rather than its base. Although relatively rare, these intense lightning bolts have up to 10 times more electrical energy than typical lightning strikes. “Because they carry enough energy to travel, say, 50,000 feet to the ground, the thunder that accompanies them will often be a batch stronger.”

There are also thunderclaps, which are loud, explosive thunder sounds that can accompany extremely close lightning. It’s basically thunder that hits your ears before it has had time to reverberate and echo.

Or you may hear thunder as a long, low-frequency boom. This often occurs when lightning strikes a few kilometers away. As sound waves from the thunder resulting from lightning travel, the atmosphere naturally absorbs their higher and higher frequencies. What remains are the deep, bass tones of thunder.

Ultimately, the louder the thunder, the closer the storm is. The National Weather Service warns that if thunder is heard in all, It is usually within striking distance of the storm. This means that lightning can strike anywhere around you (even if it’s sunny), so it’s best to take shelter indoors.

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