Thunder Equals Downpour

"Felt the lightning

And we waited on the thunder

Waited on the thunder

I woke last night to the sound of thunder

How far off I sat and wondered"

- Bob Seger, Night Moves

Weather in TV Land is weird. It strikes with no warning or buildup, and can stop just as suddenly. The most common example is a loud thunderclap, followed instantly by a drenching downpour (sometimes a single raindrop in between them). No wind, no sprinkling rain, nothing beforehand to warn our unsuspecting characters that they need to get indoors.

Often combined with When It Rains, It Pours. Contrast A Storm Is Coming.

Film - Animated
"Jane: I'm in a tree with a man who talks to monkeys!
 * Tarzan: When Jane is stuck in the treetops with Tarzan:


 * After she gets stuck between two branches*

Jane: It can't get any worse, can it?


 * Thunder, instant downpour*

Jane: Obviously, it can."


 * When Emperor Kuzco is left alone in the forest in The Emperors New Groove, this happens.

Literature
"Of a sudden there was a sad, low moaning through the surrounding trees; dense, black clouds obscured the radiant moon; and then with hideous thunder and vivid flashes of lightning the tempest broke in all its fury of lashing wind and hurtling deluge. It was the first great storm of the breaking up of the monsoon, "
 * In the Warrior Cats graphic novel Beyond the Code, there's a couple of clouds in the sky as the full moon shines down on the Gathering. The cats comment how the drought might end since the the weather's cooler. An argument starts, and one cat runs away in anger. There's a flash of lightning and a KABOOM, and it's a downpour. Enough of a downpour to actually create a flood that fills this gorge to just a few feet below the clifftops.
 * In Edgar Rice Burroughs's The Monster Men, after the attack, this happens.

Film - Live Action

 * The Great Race: Max warns Professor Fate that there's going to be a storm because of the "red sky", thunder follows, the the rain comes pouring down.
 * In The Frisco Kid, after Rabbi Avram tells a skeptical Native American chief that the Abrahamic God can do anything, "but he does not. Make. Rain.", there's a thunderclap and a downpour.
 * In The Two Towers, at Helm's Deep, just before the battle is engaged, the two armies face each other... and you hear thunder, there are a couple of raindrops on armor, then the downpour begins. Theoden is very not happy about it; some of the movie's extra material implies that the storm was raised by Saruman for the specific purpose of demoralizing the Rohirrim.
 * Used for dramatic effect in Enchanted, when Giselle comes to the Real World for the first time. After being completely lost and having her tiara stolen by a homeless guy, she stands helplessly in the middle of the street, hears thunder, and gets poured on from above.
 * The Truman Show: When Truman is sitting on the beach reminiscing, there is a clap of thunder and it begins to rain, but only where he is sitting. He walks three feet before turning around in shock to see the small column of rain as it follows him.
 * Averted in the first Back to The Future, when the storm just completely stops right after the lightning hits the clocktower. However, it's played straight in the sequels--with the exact same storm.
 * Not exactly averted, but weird nonetheless. At the end of the second movie, the lightning and wind is going nuts, but once the De Lorean is struck and disappears, the lightning and wind stops, and then it starts to pour. That's one crazy storm.
 * Young Frankenstein features a classic comedic example during the grave-digging scene, after Igor makes a most unfortunate comment about the lack of rain.

Video Games

 * Agarest Senki 2 does this trope in full effect at the start of the game.