Basically, the weather is just wrong for what it's supposed to be. Usually it's because of something like a Weather Control Machine, sometimes it's from an identifiable source like global warming or "El Niño", but sometimes it's just because we can't perfectly predict the weather. It's just too damn complex.
Weather can be just off, with no explanation. This is usually Empathic Environment or a significiant hindrance to what the characters intend. Law of Conservation of Detail ensures that strange weather can not be just a background detail. Anyway, the Weather Report certainly isn't going to predict this.
Note that unusually good weather can also be Weather Dissonance. Unexpected rain in the desert or drought-stricken land, unexpected sunlight in the fog and cloud—it can be ironic, or a good omen, or the Empathic Environment responding to the Happy Ending.
If cold temperature is involved, then Snow Means Cold is likely to occur.
- It starts snowing in August in Digimon Adventure.
- In Marvel Comics, the Casket of Ancient Winters was opened in the Simonson Thor era. This ended up being a godsend for continuity-mad fans to explain away appearances of winter weather in other comics that couldn't have actually happened in winter because of the floating timeline.
- Storm tends to whip up fogs and tornadoes to suit her purposes, and then there's the time Dr. Doom turned her into a living statue. Claustrophobia + Weather Powers = continent sized class 5 hurricane.
- In the film White Christmas, much of Vermont is in a warm spell, despite being ski season.
- The rain of frogs at the end of Magnolia.
- In Animal Crackers, Chico and Harpo Marx avoid having to go out in a thunderstorm by taking an alternate exit into a sunny garden.
- Near the end of How to Train Your Dragon Hiccup describes the climate along these lines: "It snows nine months out of the year and hails the other three." And yet it's been bright and sunny the entire film.
- It even rains in one scene!
- That was hyperbole. In the beginning, Hiccup narrates (falsely, for dramatic purposes) that the place he lives is perfect, aside from the awful dragons. In the end, he turns it around by saying (falsely, for dramatic purposes) that the dragons are the only remotely tolerable thing about his home.
- Happens all the time in the Weather Wardens books, for obvious reasons. Also, the weather tries to kill humans.
- To expand on this, it is stated several times across the novels that natural disasters are supernaturally drawn to Wardens. It is implied at times, and outright stated at others, that humanity did something millenia ago that pissed off Mother Nature so much that she has spent the ensuing time trying to wipe us off the face of the planet. The Wardens spend most of their time staving off these disasters...until things take a turn for the worse, mainly due to a few characters actively trying to destroy the world, open a portal to Hell, and possibly summon up a being older than the universe.
- In Ursula K. Le Guin's Wizard of Earthsea, the first ability Ged shows is summoning a mist against a raiding party. Other wizards can control the wind (helpful when sailing among islands) and it was common for a rainstorm to go zigzagging over an island until it reaches the sea where it can rain in peace, without a wizard under it. Ged's mentor, on the other hand, was a wise soul who would let it rain on him.
- In Dan Abnett's Gaunt's Ghosts novel Ghostmaker, the Ghosts are repeatedly hit with Chaos-inflicted weather. Once it downed Gaunt's shuttle, leaving Corbec in command for the first time. At the end of the novel, an eldar summoned a storm to provide shelter for the regiment he wanted to use; it ran wildly and killed many of the troopers.
- Similarly at the end of Honour Guard, the arrival of Chaos forces was pressauged by a terrible storm.
- In Blood Pact, the snow. Not too anomolous. On the other hand, it stops during actual attacks by Chaos forces.
- Inverted in Thief of Time, when Igor and Jeremy need a thunderstorm to start the Glass Clock. Jeremy keeps claiming that they don't have one (for reasons of his own, mostly to spend more time with Myria Le Jean), but Igor points out that they have had several available in the last few weeks, none of which Jeremy has used.
- Dan Abnett's Warhammer 40,000 novels.
- In Brothers of the Snake, rainstorms hit a desert planet during a coronation. At first this is taken as a good omen, but as it grows serious, the people are disturbed and riot. Chaos forces had assassinated the old queen in order that the Requisite Royal Regalia might be removed from what it was protecting.
- In the Horus Heresy novel Horus Rising, one planet has "shield storms" arising when the Space Marines arrive. Caused, it turns out by trees.
- Poul Anderson's Operation Chaos opens in the rain because the enemy had taken out the (magician) Weather Corps with a lucky shot. The sole survivor was keeping off the dangerous weather, but other than that, they had to take what the enemy threw, and this time, it was rain.
- In Graham McNeill's Horus Heresy novel False Gods, Davin's moon goes all the way to Climate Dissonance. It's supposed to be hot and dry, and forest where they land. They arrive in the fog to find a landscape of marsh and swamp.
- Inverted in Good Omens: one of the odd things about the Antichrist's home town was that it always had normal weather for the time of year... the one thing you don't expect in England.
Newt: "When do you remember normal weather for the time of year? Normal weather for the time of year isn't normal, Sergeant. It has snow at Christmas. When did you last see snow at Christmas?"
- In Jim Butcher's Dresden Files novel Small Favor, early and heavy snowfall. Harry suspect that Queen Mab sent it as a favor to him, to keep Summer fae from being able to overwhelm him.
- Harry does concede, however, that it could just be Chicago being Chicago.
- In Ghost Story, there's heavy snow in Chicago in May. This is because Mab is in town, specifically, on Demonreach, keeping Harry's body alive.
- Used a bit strangely in Cloudy with a Chance of Meatballs, where the tiny town of Chewandswallow never got normal weather, but instead all their food came from the weather (usually falling like rain, but things occasionally blew in, and a jell-o mold set in the west). The Film of the Book made this the result of a Weather Control Machine.
- In the Season 3 episode "Amends" of Buffy the Vampire Slayer, it snows in the Southern Californian town of Sunnydale.
- This trope is more or less half the plot of the second Touhou Project fighting game, Scarlet Weather Rhapsody. Each weather type also has an effect on the game's mechanics.
- Before this, the plot of Perfect Cherry Blossom starts with snowstorms still occurring in May.
- Can potentially happen in the Total War games, with intense rainstorms in the desert or snowstorms. You can actually try to control the conditions a little bit using the "wait" option during deployment, which can be useful to avoid battlefield-covering fog - unless, of course, you want fog, rain, or snow for dramatic reasons.
- Pokémon Ruby and Sapphire had, towards the end of the plot, one of the Olympus Mons go berserk and causing either a drought with intense sunlight, or a vicious storm in the eastmost part of the world.
- And Pokémon Black and White games we have Thundorous and Tornadus, that cause violent downpours wherever they go, be they routes bording deserts or open sea.
- The opening of NieR sets off the whole post-apocalyptic thing nicely by having the city covered in snow. Then pointing out that it is the middle of summer.
- As part of the central gameplay mechanic in Persona 4, mutiple segments are dedicated to watching fog roll in Inaba after a constant rainstorm. This fog comes from a point in which the Midnight Channel has an overflow of fog, which rolls over, causing an extremely dense fog in Inaba, even in the middle of summer. It eventually becomes lampshaded when the local weather channel decides that this phenomenon is bad for public health and warns the people, which is partially correct due to the people thrown within the TV end up with lowered stamina, but this is otherwise Insane Troll Logic. The True Ending route takes this one step further: an unusual fog creates a "Cloudy Day" that would have lasted forever if taken the OK/Bad Endings, and it's the exact same kind as the Midnight Channel's.
- An episode of Boondocks features a 90-degree Fahrenheit day and its effects on the people of the neighborhood - only to have those effects rapidly undone when it turns out that it's February and it starts abruptly snowing. Suddenly Huey doesn't look so out of place in his heavy coat he's been wearing the whole time.
- A Boy Scout troop in Southern Wisconsin is nicknamed 'The Rainmakers', and even displays the name proudly on their T-shirts. They picked up the moniker when it rained during every single campout they went on for several years straight.
- Calgary. Blizzards in June, heat waves in January, sixteen inches of rain in two days followed by two years of drought...
- According to Forbes, Springfield, Missouri is the city in the United States with the most varied weather. It's a combination of higher elevation than the surrounding regions, being landlocked, and right on the edge of tornado alley.
- On January 11, 2008, snow fell in Baghdad for the first time in a hundred years.