What it does
Cloud Nine suppresses all active weather effects while the holder is on the field. Weather is still in play — it won't end early — but every bonus and penalty it produces shuts off. Rain's ×1.5 Water boost and ×0.5 Fire penalty vanish. Sun's Fire boost disappears. Sandstorm chip stops. Snow's Ice Defense boost pauses.
The speed-doubling effects tied to weather — Swift Swim, Chlorophyll, Sand Rush, Slush Rush — also stop working while Cloud Nine is active. The opponent's rain sweeper with Swift Swim reverts to its base Speed the moment Altaria enters. When Altaria leaves, it doubles again.
Who runs it
Altaria (98%) is the primary Cloud Nine user and carries it mainly as a side benefit — its Dragon/Flying typing, bulk, and Mega Evolution option are why it's picked at 98%. But that means weather suppression comes bundled for free. Rain team, sun team, sand team: the moment Altaria is on the field, all their weather-dependent accelerators stop.
Drampa (89%) functions similarly. High usage for its own offensive and support merits, with Cloud Nine as built-in tech against weather-based opponents.
How to use it
The direct play: in team preview, when you see a weather team, prioritise getting the Cloud Nine holder on the field during the turns the weather team wants to execute. Their Swift Swim Pokémon's doubled Speed disappears. Their Chlorophyll Pokémon slows down. Their whole timing plan stops working.
In doubles, this creates a back-and-forth: your opponent switches their Cloud Nine answer in, the effects return; you switch back, the effects stop. That switching costs them actions and HP. Weather teams rely on sustained weather execution — every interrupted turn is a loss.
Altaria's Mega Evolution (Pixilate) lets it do real damage while simultaneously suppressing weather, which means a single team slot handles both jobs.
Tips & strategy
Air Lock is mechanically identical to Cloud Nine — same full weather suppression, just a different name (seen on Rayquaza). Same effect, same rules.
Cloud Nine also stops sandstorm chip for every Pokémon on the field — yours included. Running a team that doesn't enjoy sand damage? Landing a Cloud Nine holder against a sand team removes the chip entirely without eating an item slot on Safety Goggles.
The 98% Altaria usage tells you the right framing: Cloud Nine is a bonus, not the reason. Teams are built around Altaria's other qualities; weather suppression shows up as a consequence.