Whether to Weather the Weather - Weather Teams

Regardless of whether you were disoriented by the title or not, there's no doubt that weather teams certainly exist in Pokémon's competitive world. Summoning a sandstorm, rain, hail, or fierce sunlight can be a serious perk to your team. Why? Well, let's take a look.

First, it's worth noting that weather boosts certain types of moves and grants other beneficial or non-beneficial effects:
- Intense sunlight boosts Fire-type moves by 50%, allows Solar Beam to go off in one turn instead of two, changes Weather Ball's type to Fire and doubles its power, makes Cherrim change form, makes it impossible for a Pokémon to be frozen, and makes Morning Sun, Synthesis, and Moonlight recover more HP.
- Rain boosts Water-type moves by 50%, grants Thunder and Hurricane the ability to bypass their accuracy checks (they will always hit unless blocked by Protect/Detect/etc), activates Dry Skin, Swift Swim, Forecast, Hydration, and Rain Dish, changes Weather Ball to Water-type and doubles its power. It also weakens Morning Sun, Synthesis, and Moonlight, as they recover only 25% of HP in rain, and also decreases Solar Beam and all Fire-type moves' strength by 50%.
- Hail activates Forecast, Ice Body, and Snow Cloak, allows Blizzard to bypass accuracy checking, and changes Weather Ball to an Ice-type move and doubles its power. It damages all Pokémon that are not Ice-type (or have an Ability that allows them to bypass that damage), reduces the effect of Morning Sun, Synthesis, and Moonlight to the same percentage (25% recovery) as in rain, and weakens Solar Beam to 50% power.
- Sandstorm activates the Abilities Sand Rush, Sand Force, and Sand Veil. It raises the Special Defense of all Rock-type Pokémon by 50%, and changes Weather Ball to a Rock-type moves and doubles its power. Sandstorms damage all Pokémon that are not Rock, Ground, or Steel type, do not have an Ability that allows them to avoid the damage, and that do not hold Safety Goggles. Solar Beam will deal 50% of its normal damage in a sandstorm, and Moonlight, Synthesis, and Morning Sun only heal 25% of a Pokémon's health.

If your team is specialized to work well in a certain type of weather due to their types and/or Abilities, or is designed to play directly off of weather to boost/diminish moves' power to their advantage, the team can be considered a "weather team." The most common weather teams tend to be rain and sandstorm teams, though with the Drought Ability, sun-based teams are beginning to become more prevalent in Generation 6.

How Can Weather Be Summoned?
For the sake of simplicity and relevance, I'll only be talking about the means by which weather can be summoned in battle. Weather can be summoned by a specific move or Ability, which differs from weather type to weather type.
Moves that summon weather are:
- Sunny Day
- Sandstorm
- Hail
- Rain Dance
I'm sure that you can figure out which move corresponds with which weather type.
Abilities that summon weather, and the Pokémon that possess said Abilities, are:
- Sand Stream (sandstorm, five turns; Tyranitar [and Mega], Hippopotas, Hippowdon)
- Drought (intense sunlight, permanent; Ninetails H, Vulpix H, Mega Charizard Y, Groudon)
- Drizzle (rain, permanent; Kyogre, Politoed)
- Snow Warning (hail, permanent; Snover, Abomasnow [and Mega], Amaura H, Aurorus H)

It's worth noting that these "permanent" weather conditions actually aren't permanent; they just last until they're replaced by something else. It's also worth noting that, if a Pokémon has an H next to its name, the ability in question (Snow Warning/Drought) is its Hidden Ability, obtainable through the Dream World/Friend Safari/Horde battle.

So, there you have it. Whether you're developing your own weather team, or a team that can just weather the weather, you might have a better picture as to what type of weather best suits you. (OK, I'll stop with the weather puns now.)

(As a final note, it's worth mentioning that, if you're sort of patient, you can get Politoed in Pokémon Y & X by fishing on Route 19 with the Super Rod. The normal method of evolving Poliwhirl into Politoed involves trading it whilst it holds a King's Rock; if you really want the adorable little beast that is Politoed, go fishing! (Bring plenty of Ultra Balls, particularly if your Pokémon are over-leveled.)

(Via Bulbapedia.net)