Battle effects

Most arenas have a battle effect: a weather and/or a terrain that is active from turn 1 for the whole battle. A move or ability can replace it (Rain Dance in a sun arena, a lead with Drought or Grassy Surge), and from then on it behaves like normal weather or terrain. Check the arenas in the veto and build your team around the ones you pick.

Which arena has which effect: see Arenas.

Weather

Affects every Pokémon on the field.

Sun

Lava

Fire-type moves deal 50% more damage; Water-type moves deal 50% less.
Solar Beam and Solar Blade fire without a charge turn.
Pokémon can’t be frozen. Thunder and Hurricane drop to 50% accuracy.
Synthesis, Morning Sun and Moonlight heal more. Abilities like Chlorophyll and Solar Power activate.

Rain

Water

Water-type moves deal 50% more damage; Fire-type moves deal 50% less.
Thunder and Hurricane never miss.
Solar Beam and Solar Blade deal half damage. Abilities like Swift Swim and Rain Dish activate.

Sandstorm

Desert

Rock-type Pokémon get +50% Special Defense.
At the end of each turn, Pokémon that aren’t Rock, Ground or Steel lose 1/16 of their max HP.
Abilities like Sand Rush, Sand Force and Sand Veil activate.

Snow

Ice

Ice-type Pokémon get +50% Defense.
Blizzard never misses. Aurora Veil can be used.
No chip damage. Abilities like Slush Rush and Ice Body activate.

Terrain

Only affects grounded Pokémon: Flying types, Pokémon with Levitate and Pokémon holding an Air Balloon aren’t affected (unless Gravity is active).

Grassy Terrain

Forest

Grass-type moves used by grounded Pokémon deal 30% more damage.
Grounded Pokémon heal 1/16 of their max HP at the end of each turn.
Earthquake, Bulldoze and Magnitude deal half damage.

Electric Terrain

Factory

Electric-type moves used by grounded Pokémon deal 30% more damage.
Grounded Pokémon can’t fall asleep.

Psychic Terrain

Not used by an arena yet

Psychic-type moves used by grounded Pokémon deal 30% more damage.
Grounded Pokémon can’t be hit by priority moves like Quick Attack or Sucker Punch.

Misty Terrain

Not used by an arena yet

Grounded Pokémon can’t get status conditions (burn, poison, paralysis, sleep, freeze) or confusion.
Dragon-type moves deal half damage to grounded Pokémon.

Field effects Planned

The battle engine supports these too. They change battles a lot more than weather, so they’re meant for special event arenas and aren’t used in ranked.

Trick Room

Slower Pokémon move first within the same priority bracket.

Gravity

All moves become more accurate; Flying types and Levitate Pokémon are grounded, so Ground moves hit them.

Magic Room

Held items have no effect.

Wonder Room

Every Pokémon’s Defense and Special Defense are swapped.