People need to learn this as fast as possible, you cannot slap weather related abilities and expect them to be good at it. Lets clarify why.

Lets look into pelipper and what made it such a game changer that weather setters like gigalith, torkoal and ninetales (until this gen) were not when they were introduced. Its not just because rains brings more advantages than other weathers, no, its about what pelipper provides. Pelipper provides pivoting, which allows it to retain momentum, does that mean that all is needed to be a good setter is pivoting? No. Pelipper provides another key aspect to rain: a water type that can also threaten grass types from switching in/staying due to its flying type throwing out accurate hurricanes. It also posses defog, which it can fit to help its team even further. Pelipper provides actual advantage to rain teams which makes it useful in the team rather than just being a slot that provides the weather.
Now lets look into abusers with weather-related abilities and what they bring to the table:

Putting these three together since they are rain-based, but they have some really important differences about the usage. Let's start with mega swampert in gen 7 and gen 8 national dex. In these metas, Swampert is the biggest asset of the rain team, as it is what justifies running rain. It is an brutal sweeper with a high attack and a lot of speed under rain, providing a way to break through opposing team structures with its damage and speed control with its swift swim. It also provided a key aspect that actively helped its team instead of just speed and attack: A eletric neutrality. This meant that one of the key weakenesses of rain in electric types was an issue that rains would not struggle against. After its departure, Barraskewda and Seismitoad were able to provide each aspects that were previously covered by swampert. Seismitoad provided the needed electricity inmmunity and rocks support that pert gave before, while barraskewda provided the pure breaking power and speed control that made rain so threating, to the point of still being used on rain even in national dex alongside pert.

Arctozolt is to hail what swampert/barraskewda is to rain. Ninetales had always being a good hail setter with its previously exclusive aurora veil, but it had nothing to actually have hail be used. Arctozolt is the mon that catapulted hail to stardom. Sure, it lacks proper defensive utility so it doesn't help its team defensively that much, but zolt is able to accomplish what every slush rush mon before it had failed to do: break through bulky waters and other fat mons that walled hail relentlessly, as well as being a generally powerful mon thateither breaks holes on the opposing team or makes use of the holes created by its teammates to accomplishbrutal sweeps.

Excadrill may no be seeing the best of days these days, but it is crucial to remember what he used to be for sand for so long. Exca was a terrifying sweeper with its sand rush set, but that wasn't the only thing exca could provide. Exca itself is a fantastic mon even without having sand, which meant that sand would not be relying on a mon whose onlyworth was on sand. Excais also a pretty decent spinner which helps sand teams get rid of hazards, as well as set up rocks for the team.
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