I'll be updating/creating a weather team guide, similar to D_A's stall team guide that's currently in the compiled guides thread. Weather is just so profound and abused in this meta that there should be something about it.
topics will include:
- what exactly defines a weather team
- how pokemon can benefit from each weather & intro to weather starters
- good weather abusers
- structure of a weather team
- starter vs starter matchups (aka ttar/hippo vs toed vs abomasnow vs tales)
---^ how to keep your starter alive at all costs!
- how to deal with weather teams if you're not running one
- other threats to weather teams
- ...some other stuff that i wanted to have in here but icr right now so i'll edit in later
this post will be frequently updated with whatever i'm writing so yeah! :]
An Introduction to Weather Teams
Generation V completely changed the definition of "weather" teams from Generation IV. Previously, Sandstorm was the reigning king due to the prevalence of Tyranitar and Hippowdon, two very effective Pokémon who had the ability Sand Stream (an automatic Sandstorm-starting ability). Abomasnow had one in Snow Warning, but it simply wasn't as good at the time. Rain Dance and Sunny Day teams, while effective, were significantly hurt in OU because of the popular weather-starters that could break their game.
But Generation V gave older Pokémon new abilities through Dream World, as well as introducing two entirely new weather-related abilities. Offense has gradually shifted to "weather" teams and "not-weather" teams. Weather has become such a dominating force in Generation V that the generation itself is often referred to as "weather wars". Well-built and effective weather teams are nearly impossible to stop. Weather has introduced many new Pokémon to the metagame whose purpose are simply to check out-of-hand weather sweepers. And weather isn't all offense, either - Sandstorm and Hail have always been effective stall machines, and new Rain Dance and Sunny Day teams have begun to adapt themselves to stall as well. There's so much you can do with a weather team that you simply cannot do everything that a weather can accomplish in one team.
This article is a guide to show you how to maximize your potential when using a weather team, as well as how to handle specific threats to weather including other weather teams. It's also here to give you various tips and guidance to help you build your own successful weather team. Lastly, this article is here to show non-weather teams how to handle the high intensity and pressure that weather teams create.
Wait, what is weather? Why do I need to know about it?
Firstly, weather is what's known as a field condition. When it comes into play, it brings special effects with it for both players in a match. When a move like Sandstorm, Hail, Sunny Day, or Rain Dance is used, the field condition lasts 5 turns (8 turns if you use their respective items like Damp Rock). However, with the start-up abilities like Drought, Drizzle, Snow Warning, and Sand Stream, that particular weather stays in play
for the rest of the match. This is why these weather-starters are so important - whenever yours or your opponent's comes in, it can completely flip around whatever advantages you or your opponent had. Remember, no two weather effects can be up at the same time - if it's Sunny and your opponent's Tyranitar comes in, whatever benefits you had from your weather is lost because Sandstorm gets started up. But what effects do each of the weathers have? What benefits from these effects? And how can you utilize them properly? This is where we begin individual sections - explaining each weather, Pokémon that benefit from it, and playstyles that result from that. First up is Sand Stream!
Sand Stream (which introduces the weather Sandstorm) was the most prevalent weather condition in the last generation. It's two starters, Tyranitar and Hippowdon (first and last Pokémon up there, respectively) were great Pokémon to be using, and Sandstorm's residual damage benefited many a team. It strongly discouraged the use of any other weathers because of how common those two Pokémon were - if you went through all of the effort to get an 8-turn Rain Dance set up, one of these guys switching in ended it all 7 turns early.
The biggest and most important effect that Sandstorm has is its residual damage. Any Pokémon that isn't Rock-, Ground-, or Steel-type and/or has the Sand Veil ability takes 6.25% damage at the end of every turn. This may not seem like much when you consider that an opponent has 93.75% health after being hit by Sandstorm once, but there are some huge implications that go along with this. For offensive teams, Sandstorm cancels out opposing Pokémon's Leftovers, meaning that defensive Pokémon without recovery cannot take damage as well and makes them easier to break through. Defensively, Sandstorm damage plus Life Orb recoil plus entry hazard damage really compounds on a Pokémon and wears them down that much faster. A second important mechanic that Sandstorm causes is that all Rock-type Pokémon (no, not Ground- or Steel-types) gain a 50% boost to their Special Defense. This is most commonly abused with Tyranitar, but most Rock-type Pokémon have poor Special Defense, meaning this boost is gladly accepted.
Sandstorm also has an effect on several moves that change due to weather:
- Thunder: Accuracy decreases to 50%
- Solarbeam: Accuracy decreases to 60% and requires a turn to charge up
- Weather Ball: Power changes to 100 and becomes a Rock-type move
- Synthesis/Morning Sun/Moonlight: Amount recovered becomes 25%
Drizzle / Rain Dance 
Drought 
Snow Warning 
dark horse ^