What is thunder and using the 5-second rule

Added: 2026-06-06

[00:00:00]Lightning is what we see during a thunderstorm. I'm going to focus on a thunder as it is that what we hear after the fact. So, I'll break down exactly why we hear thunder go boom, and also the 5-second rule behind that.

[00:00:13]Now, why thunder exactly makes the noise and booms like it does, well, we start off with talking about lightning. That is the first reaction, and lightning is extremely hot. In fact, 54,000° Fahrenheit, which is five times hotter than the sun. So, this is what happens.

[00:00:30]Heat surrounds the area quickly. That is a very, very hot bolt of lightning hitting a not very hot surface. So, what happens is when we talk about science, when something heats, it expands, and this expansion happens very quickly.

[00:00:44]That then happens explosive. So, because it's so quickly, it's an explosive reaction that's occurring. This creates a shock wave that is similar to a sonic boom. So, the air in front of that explosion then compresses, that creates that sound wave and that sound that occurs with that thunder.

[00:01:03]So, in normal conditions, this is also going to be something that temperature will impact. When temperature is in normal conditions, warmer air means faster motion. So, air typically decreases with height, which means you would normally be able to hear thunder mentioned by about 10 to even 15 miles.

[00:01:22]But, there are times, especially during maybe winter months, that there can be what we call an inversion.

[00:01:28]When air temperature increases with height, so sometimes that can happen where we'll see a little bit in the atmosphere where maybe cooler on the surface than all of a sudden there might be a quick increase and then back to cooling.

[00:01:40]That's where we could see that temperature inversion impact the sound waves and refract them or bend them back towards the Earth's surface.

[00:01:47]That means only maybe some direct thunder will be heard, and that means this will decrease how far the distance you might be be to hear some of that thunder.

[00:01:57]However, in some cases that may amplify some sounds with that refraction, but typically when there is that inversion in place, usually only direct thunder will be heard.

[00:02:08]Now, as we look at the 5-second rule, this is going to be something that really plays a part especially in those summer months when you're trying to find out how far away lightning is. So, apply a little bit of a math game here.

[00:02:20]So, this again helps you really kind of a in easy way to see how far lightning is away. It gives you a better idea to keep yourself safe if you're outside especially. So, you see a lightning strike or you see maybe that flash of light in the air and you want to see how far it is.

[00:02:37]You start counting when you see the lightning. So, you count the seconds.

[00:02:41]So, count one Mississippi, two Mississippi, and so forth. You stop counting when you hear the thunder.

[00:02:47]You take that number that you counted, then you simply you divide it by five.

[00:02:52]So, we look at that rule and we apply it. We can try it a few times here. You count to five, that would mean you get a mile cuz five divided by five is one. If you count to 10, that'll make it 2 miles away.

[00:03:04]And so on and so forth. And that would break down the 5-second rule for you.

[00:03:08]And that will also help you keep you and your family safe as you're maybe outside, if you're maybe playing with your friends. Those kind of things help you keep safe during those summer months. Reporting for Storm Team 27, I'm meteorologist Hannah Erdman.