Weather

Weather is an important aspect of dungeons and should always be taken into account as it impacts gameplay and dungeon difficulty. Ιt also affects the aesthetics of the overworld.

Weather occurs naturally in most dungeons or is triggered by enemy Pokémon's Abilities. Obviously, most enemy Pokémon in a dungeon are adapted to the local weather and benefit from it. For example, Pokémon with Sand Veil are often present in Sandstorm. However, the player can break this synergy by taking advantage of the local weather or by changing the weather to their own advantage. In general, creating weather-based synergy within the team or party can significantly boost chances of survival in tough dungeons and reduce conflict "weather fights".

Players can change the weather themselves through moves, Abilities and weather rocks. A weather condition lasts until entering the next floor or until someone else changes the weather (e.g. a Drizzle Pokémon spawning or a Cherrim using Sunny Day). Weather moves can be used any time, but weather Abilities require the Pokémon to enter the floor to be triggered. Weather rocks are items that need to be held by a team member to give a weather condition effect to the player only, provided that the external weather is clear (except for the Clear Rock that overwrites other weather conditions). Weather rocks can be purchased from the Dark Market in Tanren Undercity, and found in certain dungeons. In PMU, weather is also crucial because it activates Gems and Crystals. These are bag items that give significant buffs to your team's Pokémon of the same type, by granting immunity to status problems and by giving a movement speed increase to that type respectively. Since PMU is real-time, rather than turn-based, and status problems are very common, Gems make a great deal in planning out a strategy. PMU 7 features the weather conditions encountered in PMD and the core series. There are a total of 9 different weather conditions (10 if clear weather is considered), each with different gimmicks. Most conditions buff or nerf a particular Pokémon type, but also have general effects that affect all types. In this sense, some family items activate only during particular weather conditions.

It's important to note that moves which never miss in certain weather only take in account what condition the enemy Pokémon is in. For example, holding a Damp Rock in clear weather will not make Hurricane bypass accuracy. This means, however, if it were raining while holding a Clear Rock, Hurricane will bypass accuracy.

Clear
Clear weather is the standard weather and has no particular effects. It is crucial for the activation of weather rocks.
 * Cannot be triggered by moves
 * Typically used in conjunction with weather rocks
 * Triggered by the Ability Cloud Nine (Golduck, Lickilicky and Altaria lines, Drampa)
 * Triggered by the Clear Rock when held. Does not stack with other weather rocks
 * Triggered by the Clear Sky Orb
 * Activates family items that require clear weather
 * Activates the Fight, Sky, Guard (Bug), and Dragon Gems and Crystals

Cloudy
Cloudy is considered the weather for Normal-types; it essentially nerfs all types but Normal. Cloudy weather via the weather rock does not include the damage reduction.
 * Cannot be triggered by moves or Abilities
 * Triggered by the Cloudy Rock in clear weather
 * Triggered by the Cloudy Orb
 * Halves damage of non-Normal-type moves
 * The move Weather Ball has its power doubled
 * Reduces HP regained by Morning Sun, Moonlight and Synthesis
 * Activates family items that require cloudy weather
 * Activates the White (Normal), Poison, and Thunder Gems and Crystals

Rain
The weather that buffs Water-types and nerfs Fire-types.
 * Triggered by the move Rain Dance
 * Triggered by the Ability Drizzle (Politoed, Pelipper, Kyogre)
 * Triggered by the Damp Rock when held in clear weather
 * Triggered by the Rainy Orb
 * Increases damage of Water-type moves by 1.25x
 * Halves damage of Fire-type moves
 * Halves damage of the move Solar Beam
 * The move Thunder will never miss
 * The move Hurricane has its accuracy increased
 * The move Weather Ball becomes Water-type and has its power doubled
 * Reduces HP regained by Morning Sun, Moonlight and Synthesis
 * Activates the Abilities Swift Swim, Hydration, Dry Skin, Rain Dish, Forecast
 * Activates family items that require rain
 * Activates the Aqua Gem and Crystal

Sunny
Opposite to rain, this weather buffs Fire-types and nerfs Water-types. Additionally buffs Grass-types and Fairy-types, creating good synergy between the three types.
 * Triggered by the move Sunny Day
 * Triggered by the Ability Drought (Ninetales line, Torkoal, Groudon)
 * Triggered by the Heat Rock when held in clear weather
 * Triggered by the Sunny Orb
 * Increases damage of Fire-type moves by 1.25x
 * Halves damage of Water-type moves
 * Halves the accuracy of the moves Blizzard, Thunder and Hurricane
 * The move Weather Ball becomes Fire-type and has its power doubled
 * Increases HP regained by Morning Sun, Moonlight and Synthesis
 * No recharge time for the move Solar Beam and Solar Blade
 * The move Growth raises Attack and Special Attack by two stages
 * Activates the Abilities Chlorophyll, Dry Skin, Flower Gift, Leaf Guard, Solar Power, Forecast, while buffing Harvest
 * Activates family items that require sun.
 * Activates the Fiery, Grass, and Pixie Gems and Crystals

Diamond Dust
PMU's unique weather, diamond dust, is the second condition to buff Fairy-types.
 * Cannot be triggered by moves or Abilities
 * Triggered by the Sparkle Rock when held in clear weather
 * The movement speed of Fairy-types increases by one stage
 * Player evasion increases by one stage
 * NPC evasion lowers by one stage
 * The move Weather Ball has its power doubled

Snow
Like Fairy-types, Ice-types are also favored by two weather conditions, in fact exclusively.
 * Cannot be triggered by moves or Abilities
 * Triggered by the Snowy Rock when held in clear weather
 * Triggered by the Snowy Orb
 * The movement speed of Ice-types increases by one stage
 * Halves damage of the move Solar Beam
 * The move Blizzard has its accuracy increased to 90%
 * The move Weather Ball becomes Ice-type and has its power doubled
 * Reduces HP regained by Morning Sun, Moonlight and Synthesis

Hail
Hail is the second condition that favors Ice-types, while nerfing all other types.
 * Triggered by the move Hail
 * Triggered by the Ability Snow Warning (Abomasnow, Amaura and Alolan Vulpix lines, Vanilluxe)
 * Triggered by the Icy Rock when held in clear weather
 * Triggered by the Hail Orb
 * All types but Ice take damage over time by walking. Pokémon with the Abilities Snow Cloak, Slush Rush, Ice Body, Overcoat, and Magic Guard are immune to this effect
 * Halves damage of the move Solar Beam
 * The move Blizzard has its accuracy increased to 90%
 * The move Weather Ball becomes Ice-type and has its power doubled
 * Reduces HP regained by Morning Sun, Moonlight and Synthesis
 * Activates the Abilities Snow Cloak, Slush Rush, Ice Body, Forecast
 * Activates family items that require hail
 * Activates the Icy Gem and Crystal

Sandstorm
Sandstorm works similarly to Hail but for the earth types. This weather buffs Rock-, Ground-, and Steel-types, thus creating good synergy between them, while nerfing all other types. It also harms the player's vision, as it makes it very difficult to navigate through the map without Safety Goggles or Sandstorm Specs.
 * Triggered by the move Sandstorm
 * Triggered by the Ability Sand Stream (Hippopotas line, Tyranitar, Gigalith)
 * Triggered by the Smooth Rock when held in clear weather
 * Triggered by the Sandy Orb
 * All types but Rock, Ground and Steel take damage over time by walking. Pokémon with the Abilities Sand Rush, Sand Veil, Sand Force, Overcoat, and Magic Guard are immune to this effect
 * Boosts the Special Defense of Rock-types by 1.5x
 * Halves damage of the move Solar Beam
 * The move Weather Ball becomes Rock-type and has its power doubled
 * Reduces HP regained by Morning Sun, Moonlight and Synthesis
 * Reduces visibility without Safety Goggles or Sandstorm Specs
 * Activates the Abilities Sand Rush, Sand Veil, Sand Force
 * Activates family items that require sandstorm
 * Activates the Stone, Earth, and Metal Gems and Crystals

Fog
The fog is the weather condition that buffs the mystical types Psychic, Ghost and Dark, while nerfing Electric-types. It also harms the player's vision. Fog weather via the weather rock does not include the damage reduction.
 * Cannot be triggered by moves or Abilities
 * Triggered by the Foggy Rock when held in clear weather
 * Triggered by the Foggy Orb
 * Halves damage of Electric-type moves
 * Halves damage of the move Solar Beam
 * The move Weather Ball has its power doubled
 * Reduces HP regained by Morning Sun, Moonlight and Synthesis
 * Reduces visibility without Safety Goggles
 * Activates family items that require fog
 * Activates the Psyche, Shadow, and Dark Gems and Crystals

Ashfall
Ashfall is another weather condition unique to PMU and buffs the Poison-type while nerfing Electric-types. It is the only weather condition that does not have a rock variant.
 * Cannot be triggered by moves or Abilities
 * Increases damage of Poison-type moves by 1.25x
 * Halves damage of Electric-type moves
 * Halves damage of the move Solar Beam
 * The move Weather Ball becomes Rock-type and has its power doubled
 * Reduces HP regained by Morning Sun, Moonlight and Synthesis

Trivia

 * While diamond dust weather is not present in the Pokémon Mystery Dungeon series' games, it is an actual weather effect in some of the main series' games.
 * Ashfall made an appearance as an overworld weather element in Generation 3 main series games. It was first introduced in PMU 7 with the release of Ash Forest.