Weather

The weather (Japanese:  weather) is a set of mechanics in the Pokémon games that change the battle environment, activating, modifying certain moves, and potentially damaging the in battle or affecting their stats. They have been included in every core series game since Generation II. In battle, weather is either determined by the location of a battle, due to overworld weather, or by a Pokémon creating a new type of weather with a move or Ability. Only one type of weather may be present at a time, and only the most recent type of weather will take effect.

In Generation II, only moves that cause weather were introduced and weather was only present in battles, not in the overworld. Generation III introduced overworld weather and weather-related Abilities, as well as a new weather-causing move. The biggest modification to weather in Generation IV was the introduction of four held items (Heat, Damp, Smooth, and Icy Rocks) that increase the duration of weather caused by or. Generation V mostly introduced greater overworld weather variability, especially in seasons affecting the weather in certain locations.

Overview
There is also a glitch that occurs in, , called acid rain, that results in the simultaneous occurrence of all then-existing weather conditions at once, damaging all Pokémon on the field.
 * Clear skies: Actually the absence of weather. This is the weather found in most locations.
 * Harsh sunlight: Strong sunlight shines on the battlefield. It is one of the rarest conditions to be seen in the overworld.
 * Extremely harsh sunlight: Sunlight shines more heavily on the battlefield. This has only occurred in the overworld in the Hoenn region, in Pokémon Omega Ruby, due to 's emergence.
 * Rain: Rain falls on the battlefield. Different variations of this weather may appear on the overworld. This is the most common weather pattern that may be found on routes and occasionally in cities.
 * Heavy rain: Rain falls more chaotically around the battlefield. This has only occurred in the overworld in the Hoenn region, in Pokémon Alpha Sapphire, due to 's emergence.
 * : Stinging sand whips across the battlefield. In Generations III through V, every new region had a specific area where a sandstorm was always occurring.
 * : Pelting hail falls on the battlefield. Different variations of this weather may appear on the overworld. There may also be benign falling snow that does not cause hail in a battle.
 * : A special, purely aesthetic version of snow. It first appeared as an easter egg in, and has appeared in several core series games since.
 * : Bursts of light rain down from a shadowy aura in the sky. This type of weather is only present in Pokémon XD: Gale of Darkness and has no overworld manifestation anywhere.
 * Fog: A thick fog clouds the battlefield. This only had an in-battle effect during Generation IV, but it has been present in the overworld in other Generations in a purely aesthetic form.
 * Mysterious air current: A strong air current blows across the battlefield. This weather can only be present in battle, as a result of 's Ability.

In Generation V, the weather was given an icon which appeared on the DS or 3DS's bottom screen in a battle whenever weather was occurring. Since fog and shadowy aura do not appear in-battle in Generation V, they have no icons. When there is no weather, no icon is shown.

In Generation VI onwards, the background of the bottom screen shows an animation of the current weather.

In Pokémon Sun, Moon, Ultra Sun, and Ultra Moon, the 3DS's bottom screen displays an icon and background animation of the current weather.

Causing weather
Most of the types of weather have a move or Ability that will cause that weather. and also suspend the effects of weather while they are active.

In addition, may clear fog from an overworld area (in Generation IV only). It is the only move that has any effect on weather in the overworld.

Weather normally lasts for 5 turns when it is called by a move. Prior to Generation VI, weather created by an Ability would continue until the battle ended or another type of weather took its place; since Generation VI, weather created by Abilities also lasts for only 5 turns, with the exception of weather created by, , and.

If multiple Pokémon with Abilities that change the weather are sent in simultaneously, the Abilities activate in order from fastest Pokémon to slowest Pokémon (or the reverse during ); this means that the slowest Pokémon's Ability will override the other Abilities.

If a Pokémon holding one of four held items creates weather that would otherwise last 5 turns, it instead lasts 8 turns. The rock that affects each type of weather is shown below.

Effects
Three of the types of weather can do damage to Pokémon in battle at the end of a turn. In a, , or , any Pokémon that is not Rock-, Ground-, or ; ; or a Shadow Pokémon (respectively) will be damaged for 1/16 of its maximum HP. Certain prevent damage from weather effects, though, and a Pokémon holding Safety Goggles is also immune to damage from weather effects.

Sandstorm and fog both affect the stats of Pokémon on the battlefield. Since Generation IV, in a sandstorm, the Special Defense of Pokémon is increased by 50%. In fog, the accuracy of all Pokémon in battle is decreased.

During harsh sunlight, all Pokémon are immune to.

Harsh sunlight and rain both affect the power of certain types of moves. Harsh sunlight strengthens the power of moves by 50% and weakens the power of  moves by 50%, while rain does the opposite, strengthening Water-type moves by 50% while weakening Fire-type moves by 50%.

Certain specific moves are also affected in special ways by the weather.
 * The recovery moves, , and will recover different amounts of HP depending on the weather: in clear skies, they recover half of the user's maximum HP; in harsh sunlight, they recover ⅔ HP; and in other types of weather, they recover ¼ HP.
 * The accuracy of, , and is affected by the weather.
 * In hail, Blizzard ignores accuracy and evasion checks, while Thunder and Hurricane do the same in rain. During harsh sunlight, however, Thunder and Hurricane only have 50% accuracy.
 * In, Blizzard and Thunder also had a 30% chance to hit through or  when used in their favored weather.
 * and become a 1-turn move in harsh sunlight, skipping its charge turn, but in rain, sandstorm, or hail, the move's power is halved.
 * From Generation V onwards, 's stat increases double in harsh sunlight.
 * When used as a field move in Generations IV-VI, will fail to work if there is a type of weather in effect in the area.
 * The move restores ⅔ of the user's total HP during a sandstorm; outside of a sandstorm, it only restores ½ total HP.

Activated Abilities
The following Abilities are activated when a type of weather comes into effect. Most of these Abilities have no effect if no weather is active.

In addition to the above Abilities, is guaranteed to restore a Berry whenever it triggers in harsh sunlight, and the Abilities  and  will prevent weather-related damage.

Castform and Weather Ball
is a Pokémon uniquely designed to take advantage of the weather. Its Ability,, causes it to change form when a type of weather is present. Forecast does not cause a unique change for every possible type of weather, though.

is a move that uniquely takes advantage of the weather. In Generation III, it was introduced along with Castform and was Castform's signature move.

Whenever there is a type of weather present, Weather Ball's base power will double to 100. Weather Ball's type also changes during most types of weather.

Because of its Ability, Castform has a unique synergy with Weather Ball that no other Pokémon that can learn Weather Ball has. In harsh sunlight, rain, or hail, Castform will always get STAB thanks to its Ability.

Weather-dependent evolution
Starting at level 50, will evolve into  if it is leveled up while it is raining in the overworld.

In the Pokémon Mystery Dungeon series
Various weather effects appear in certain dungeons in the Pokémon Mystery Dungeon series. Weather effects can change from floor to floor, and can also be altered through the use of Wonder Orbs. In Gates to Infinity, Pokémon will regenerate HP only if the weather is Clear, or if it is holding a. In, Pokémon can regenerate HP in any weather as long as they do not take damage from the weather condition, or if it is holding a.
 * Clear: None, Pokémon will restore health as turns go by
 * Sunny: Fire-type moves increase power by 50%, while the power of Water-type moves is cut in half.
 * Fog: The power of Electric-type moves is cut in half. Also turns Castform into a Water type. This weather effect is only available in the Rescue Team and Explorers games.
 * Snow: Ice-type Pokémon have an increased movement speed. Also turns Castform into an Ice type. This weather effect is only available in the Rescue Team and Explorers games.
 * Rain: Water-type moves increase power by 50%, while the power of Fire-type moves is cut in half. Also prevents explosions from traps and moves like.
 * Hail: Deals 5/3/1 points of damage to non-Ice types every 10 turns.
 * Sandstorm: Deals 5/3/1 points of damage to non-Rock, Ground, and Steel types every 10 turns.
 * Cloudy: Reduces the damage of all non-Normal-type moves by 25%. This weather effect is only available in the Rescue Team and Explorers games.
 * Harsh sunlight: Fire-type moves increase power by 50%, while Water-type moves are nullified. This weather effect is only available in Pokémon Super Mystery Dungeon.
 * Heavy Rain: Water-type moves increase power by 50%, while Fire-type moves are nullified. This weather effect is only available in Pokémon Super Mystery Dungeon.
 * Strong Winds: Moves that would be super effective against pure Flying-type Pokémon will only be normally effective. This weather effect is only available in Pokémon Super Mystery Dungeon.

Pokémon GO
Various weather effects appear in Pokémon GO, intended to reflect the actual weather that the player is experiencing. Different weathers affect certain Pokémon types, and effects include increasing their frequency of appearing in the wild, increasing the power of moves of that type in battle by 20% (rounded down to the nearest integer), and giving 25% extra Stardust when a Pokémon of that type is caught. Wild Pokémon affected by the weather boost can also appear at a higher than normal CP. Raid Bosses are also affected by weather; however, Pokémon encounters from Field or Special Research are not affected.

Sunny and Clear are the same weather type, but it is referred to as Sunny during Day Mode and Clear during Night Mode.

The form of is also affected by the weather.

Trivia

 * The Weather Institute in Hoenn is dedicated to the study of weather. It is said to have created, a Pokémon that changes with the weather.
 * All weather-creating Abilities (,, , and ) debuted the generation after their respective moves/weather (, , , and ).
 * The Generation III core games internal data contains an unused overworld weather effect of four falling snowflakes.

In other languages
Wetter Clima Climat Condizione atmosferica てんき 天气