[[quoteright:319:http://static.tvtropes.org/pmwiki/pub/images/lightning-gallery-2_9081.jpg]]
[[caption-width-right:319: BOOOOOOOOOOOOOOOOOOOM]]

FLASH! Lightning streaks across the sky! A few seconds later, the thunder arrives. BOOM!

In RealLife, thunder is the sound caused by a lightning strike. It has a delay because sound travels slower than light, and so the farther away the lightning strikes, the longer it takes for the thunder to arrive. If you do manage to hear thunder at the same time you see a lightning flash, it must probably mean that [[OhCrap you're inside the eye of storm]].

Not so in fiction. Here, lightning almost always arrives with the sound of thunder, no matter where the lightning is. This happens so often that it is remarkable when thunder does have a delay. Expect quite a few aversions to mention counting the seconds to see how far away the lightning struck, especially if the target audience is children.

Most writers, when they avert the trope, will generally include the counting to [[ShowDontTell show]] the distance of the storm.

This is such a universally used trope that only subversions and aversions should be listed as examples.

Related to DramaticThunder and ThunderEqualsDownpour. Falls under the RuleOfPerception.
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!Aversions:
* {{Averted|Trope}} in ''Film/AttackOfTheClones'', as noted in DVDCommentary.
* An unlikely aversion shows up in ''{{BC}}: The First Thanksgiving''. When a volcano erupts in the background, the resulting sound and shockwave takes several seconds to arrive.
* Not thunder, but in ''Film/MaxManus: Man of War'', two Norwegian saboteurs are observing a harbor at long range, waiting for the bombs they planted to go off. They are momentarily {{distracted|ByTheSexy}} and the viewer can see the bloom of the explosion behind them before the sound reaches both the characters and the viewer.
* ''Webcomic/TheOrderOfTheStick'': Durkon uses the Control Weather spell to create a huge lightning strike above Cliffport, which apparently doesn't harm the antagonists. The attacking animated trees (which are only vulnerable to sonic damage) [[http://www.giantitp.com/comics/oots0352.html are promptly shattered]] by the thunder which comes after a dramatic delay of "four Miss'sippi".
* The first ''Film/{{Poltergeist}}'' has the big sister teaching the little brother to count. They know the storm is coming closer as they count because the thunder comes quicker.
* ''Series/ThePuzzlePlace'' taught children to count the seconds of delay between the lightning and thunder to find out how far away the storm was.
* ''Series/{{Revolution}}'': You can see the room lighting up before you hear the thunder during a flashback in the [[Recap/RevolutionS1E8TiesThatBind 8th episode]].
* ''TheShawshankRedemption'', [[spoiler:Andy escapes from prison]] during a thunderstorm; one aspect of this involved him banging on a sewer pipe with a rock [[CacophonyCoverUp during thunder rumbles to drown out the sound]]. The thunder rumbles were almost at the exact same time as the flashes, from which [[spoiler:Andy]] knew exactly when to strike the sewer pipe.
* ''Literature/ThunderCake'' features a child and her grandma working together to gather the ingredients for a cake before the storm comes. During this they are counting the time between the lightning and thunder to figure out the time they have left.
* ''Film/TrueLies'' has a non-thunder example. The atomic blast is seen long before we hear its relatively faint rumbling. Understandable as they're at least 12 miles away, which is stated to be the minimum safe distance, though it still took a lot less than a minute for the sound to hit.
* ''Literature/TheBerenstainBears'' has counting thunder delay as a key point in ''The Berenstain Bears Count Their Blessings''.

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!Subversions:
* ''VideoGame/DonkeyKongJungleBeat'' has instant lightning. Ninja Monkeys make the wise choice of leaping into the air and raising metal objects in the middle of a thunderstorm but they will only be struck by lightning if you ThunderClap them while they do this.
* In an episode of ''Series/TheGreatSpaceCoaster'' the gang sees a flash and count to 5 (which would mean that the strike is one mile away, and thus they're not in danger). They keep seeing a flash and counting to 5 with no thunder. It turns out that it's Knock Knock the woodpecker, who is playing around with her new instant camera and always uses the flash.

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