Weather of War

Weather affecting the outcome of battles. Rain, snow, sandstorms, etc can make a big impact on strategy, used or getting screwed over by. Battle in the Rain for more than atmospherics.

This is, very commonly, Truth in Television.

See also Fog of War.

Anime and Manga

 * Nami from One Piece, even before she got her Weather Control Machine, had such an intuitive understanding of the weather that she could use it offensively, avoiding storms to which others would fall prey.

Literature

 * In The Belagariad, the Murgos use a literal Fog of War to hide their troops. In The Mallorean, Belgarion causes a lightning storm to start solely to make himself look more impressive to stop an Arend army.
 * In Belgarath the Sorcerer, during a historical battle, the enemy army sends a dust storm at them. The good guys break off a piece and send it down a nearby river and back, dropping a water spout to settle the dust.
 * The aforementioned storm sends Belgarath and his Brother Beldin running around the world for six months, dealing with the fallout. Belgarion gets quite the earful when Belgarath gets done.
 * In Dune a sandstorm not only disrupts almost any activity, but was used to exhaust Deflector Shields with tons of sand "bullets".
 * In 1635: The Eastern Front, a heavy rainstorm completely ruins the USE's invasion of Poland, taking away its technological advantages and nearly getting the emperor killed in battle.
 * In Jonathan Strange & Mr Norrell, Strange makes it rain so that the mud will hinder French cavalry.
 * In Judas Unchained, the Planet's Revenge is this taken to an extreme.
 * Two 13th century sagas, Jomsvikinga Saga and (with a little less detail) Heimskringla, tell how in the battle of Hjorunga Bay, fought in Norway c. 985 AD, the Norwegians were saved from defeat by a sudden hailstorm that turned the battle against their Danish enemies.
 * Wyatt's Hurricane by Desmond Bagley. Nothing like a really bad hurricane to interfere with everybody's plans for the revolution in a Caribbean Banana Republic. (Wyatt is the meteorologist trying to warn people that Hurricane Mabel will hit hard.) The rebel leader actually believes he can use the disruption caused by the weather.

Live Action TV

 * The Weather Channel's When Weather Changed History documentary segments sometimes invoke this trope, although natural disasters are a more common topic.

Tabletop Games

 * Some military board games have weather rules, such as Avalon Hill's The Russian Campaign, which covers the World War 2 Nazi invasion of the Soviet Union. The rules depict the difficulties the German invaders had with "General Winter".
 * Blood Bowl has weather rules. In most matches, the weather has no effect, but sometimes players can collapse in the heat, drop the slippery ball in the snow, or be blinded by the sunshine -- no matter which direction they're facing!
 * The Warhammer 40,000 canon features a battle between the World Eaters and the Emperor's Children legions of Chaos Space Marines which took place on a Daemon World. The battle was interrupted by a blizzard so severe it caused the Super Soldiers to take cover. Kharn the Betrayer of the World Eaters did not like this one bit and proceeded to, on his own burn both the World Eaters and the Emperor's Children out of their cover, breaking the ranks of both legions so severely that neither has fought as a united force in nearly 10,000 years.

Video Games

 * Planned for Achron. Which is hilarious when you think about it, because it lets you exploit your ability to observe the future for weather forecasting.
 * Rain and snow will limit your movement speed in Fire Emblem.
 * Advance Wars:
 * In the first two GBA games, rain and snow increase the cost of moving over certain types of terrain. Rain also reduced vision range by one space in Fog of War situations. Drake and Olaf's movement stats are not affected by rain and snow respectively (though Drake still took the rain vision penalty), and their CO Powers utilize them. As of the second game, Sturm's movement (not affected by snow in the first game) also became unaffected by rain.
 * In Dual Strike, weather no longer imposes movement penalties. Snow causes all units (except Olaf's) to spend double the amount of fuel to move (but allows them to move their full range), and rain induces Fog of War with the vision range reduction from the GBA games. Sandstorms reduce the maximum range of indirect combat units by one space.
 * In Days of Ruin, snow reduces maximum movement range by one space, rain induces Fog of War and reduces vision range to one space for units and zero for properties and fire pillars, and sandstorms significantly reduce attack power. Penny is immune to all of these effects (in rain, she is affected by Fog of War, but her vision range is normal).
 * In the later Dune games, a bad sandstorm can seriously damage your base
 * Several weather conditions were introduced in Pokémon Gold and Silver. Rain and bright sunlight will change the effectiveness of fire and water-typed moves, whereas Hail and Sandstorm will deal damage to all Pokemon on the field every turn unless they're a type that resists it. There are also several weather-dependent abilities as well as other moves that vary in effectiveness depending on the conditions.
 * The move Weather Ball gets power and typing depending on the weather.
 * Pokémon XD includes Shadow Sky, which damages all non-Shadow Pokemon in battle.
 * Any Total War game; rain and wind effect arrow accuracy. Snow can cause troops from northern acclimated to fight better. Storms at sea can completely wreck an invasion.
 * Each faction in Brutal Legend has a guitar solo that temporarily affects the sky above the battlefield: Ironheade's Light of Dawn cancels all enemy buffs and debuffs, the Drowning Doom's Encompassing Gloom stops the enemy from producing new units, and the Tainted Coil's Skies Afire causes friendly units to inflict more damage when they're close to their own stage.
 * In Patapon, wind can help your archer's arrows fly farther (and, if they're Arrows on Fire, help said arrows do more damage), while rain extinguishes fire but makes it possible to pass the desert.
 * The Touhou Fighting Games, starting with Scarlet Weather Rhapsody, has a mechanic where weather would change during a match, creating different effects. For example, Typhoon removes flinching and blocking, River Mist makes the distance between players go wonky, and Scorching Sun damages any player who flies too high.
 * Advanced Strategic Command has wind and weather status. Some units (mostly planes) are killed if the wind is too strong and they aren't hidden in a hangar or transport unit. Snow changes the terrain and can affect unit movement. Also, paths suffer from bad weather, while proper roads—more costly to build—don't. Output of solar and wind powerplants depends on the weather.
 * During the fight with the Hydra in Glory of Heracles DS, black rain comes down. As a result, you take damage at the end of each round.
 * High windspeeds affect aircraft performance in Earth 2150. Rain slows down ground units. Storms and meteor showers, on the other hand...
 * High windspeeds improve the performance of wind-power generators in Total Annihilation.
 * At least two separate planets and one of the moons you fight on also have meteor showers. Which can trigger units that would otherwise not have attacked yet, or destroy resource collectors. Fortunately, it's an equal opportunity damage maker, hitting player and AI alike.
 * This is one of Myth's major selling points. Strong wind can make arrows go off course, rain and wet ground might put out dwarven explosive cocktails, etc.
 * In Star Wars: Empire At War, every planet has its own weather conditions which can affect the range or accuracy of your ground units.
 * Among the natural disasters that can cause problems for you in Outpost 2 are electrical storms and vortexes, which can and will cause extensive damage to your base and any units they hit.
 * Weaponized in Command & Conquer: Red Alert 2, where the Allies had a Weather Control Satellite superweapon. Believe it or not, this was the most regular of them...
 * Meanwhile, in Tiberian Sun, Ion Storms afflicted some campaign maps and could strike at random in skirmishes. Not only did they occasionally lightning-strike random points of ground, they shut down radar, aircraft, and hovering units.
 * The Elder Scrolls V: Skyrim has a weaponized version in the form of a shout that creates an instant thunderstorm, which strikes down your foes with lightning. Another shout lets you invert this by clearing the sky, in case you want to fight under a starry sky with an aurora
 * The third playthrough of Mini Robot Wars has the enemy machines screwing around with the planet's ecosystem, causing weather hazards in every level that harmfully affect your units. Oh, and enemy units are completely unaffected.
 * Green Fields: A periodic shower of acid rain damages all topmost minirobots.
 * Waste Sands: Earthquakes occur periodically, damaging any minirobots on the ground.
 * South Ocean: Whirlpools will rise from areas without floor, damaging up to two entire columns of minirobots.
 * Glacier Land: A non-damaging blast of wind pushes back all your air units in a row. If your air units get pushed into the ground or off the right side of the screen, they are instantly destroyed.
 * Iron Fortress: "Meteors" rain down on the field, these are actually Mooks sent down from space. If a meteor lands on a minirobot, it destroys that minirobot instantly.
 * In Mass Effect 2, the weather occasionally has an impact - on several sidequests, the player encounters fog and sandstorms they cannot see through, on Tali's recruitment mission direct sunlight frys shields, and on the Shadow Broker's Base the player can use biotics to throw enemies outside the ship's environmental shield, resulting in them being flung into oblivion by the slipstream or struck by lightning.
 * In the Warlords Battlecry series, various races get various bonuses and penalties depending on the weather and time of day. Most evil races like to fight at night or in the rain (or both, e.g. the undead), while most good races like to fight during the day or with clear skies.

Real Life

 * The British defeat of the Spanish Armada was a relatively standard fleet action between Men 'O War. What made it decisive, however, was a powerful storm that swept through as the Spanish tried to regroup after the battle at Gravelines. The British merely returned to port, but the Spanish fleet was devastated—50 of their 130 ships did not return. With them, went any hope of invading England.
 * English victory and Agincourt. Due to terrain and the fact that it had rained for a few days before the battle turning the earth soft. More French soldiers died of drowning at the battle than from wounds.
 * The Normandy invasion was nearly postponed almost a month (at a minimum) except that a storm that was moving through the area was predicted to break on June 6. This allowed them both a day of good weather and a moonless night for the paratroopers. The rest is history.
 * It's a long established Running Gag that one of if not the most effective members of the Russian military is General Winter (and his trusty aide, Major Frost).
 * Both Mongol invasions of Japan were thwarted by (extremely unlikely) hurricanes, known as kamikaze (divine winds).