How does the trick with sunny day and solar beam work are there any others?

Answer 1

If it is sunny, then you can use SolarBeam without charging. Sun can be activated by either Sunny Day or Groudon's Drought ability.

These are some other effects caused by weather:

Sunlight (Move: Sunny Day or Groudon's Ability: Drought)

- The power of Fire-type moves is increased by half

- The power of Water-type moves is halved

- SolarBeam does not need to charge

- Thunder's accuracy falls to 50%

- Moonlight, Synthesis and Morning Sun recover 2/3 HP instead of half

- Pokémon with Chlorophyll have double Speed

- Pokémon with Dry Skin lose 1/16 HP each turn

- Cherrim's Attack and Special Attack are increased by half. If in a double battle, its partner also gets this bonus

- Pokémon with Leaf Guard are unaffected by burn, paralysis, poison or sleep

- Pokémon with Solar Power lose 1/8 HP each turn, but their Special Attack is increased by half

- Weather Ball becomes a 100 power Fire-type move

- Castform transforms to Sun Forme and becomes Fire-type

- Cherrim transforms to Positive Forme

Rain (Move: Rain Dance or Kyogre's Ability: Drizzle)

- The power of Water-type moves is increased by half

- The power of Fire-type moves is halved

- SolarBeam takes 2 turns to charge

- Thunder always hits and has a 30% chance to hit through Protect and Detect

- Moonlight, Synthesis and Morning Sun recover 1/4 HP instead of half

- Pokémon with Swift Swim have double Speed

- Pokémon with Dry Skin or Rain Dish gain 1/16 HP each turn

- Pokémon with Hydration are healed of burn, paralysis, freeze, poison and sleep at the end of each turn

- Weather Ball becomes a 100 power Water-type move

- Castform transforms to Rain Forme and becomes Water-type

Sandstorm (Move: Sandstorm or Tyrannitar/Garchomp's Ability: Sand Stream)

- Pokémon that are not Rock, Steel or Ground-type take damage each turn unless they have Sand Veil

- The Special Defense of Rock-type Pokémon is increased by half

- SolarBeam takes 2 turns to charge

- Moonlight, Synthesis and Morning Sun recover 1/4 HP instead of half

- Pokémon with Sand Veil have 20% extra evasion

- Weather Ball becomes a 100 power Rock-type move

Hail (Move: Hail or Snover/Abomasnow's Ability: Snow Warning)

- Pokémon that are not Ice-type take damage each turn unless they have Ice Body or Snow Cloak

- Blizzard always hits and has a 25% chance to hit through Protect and Detect

- SolarBeam takes 2 turns to charge

- Moonlight, Synthesis and Morning Sun recover 1/4 HP instead of half

- Pokémon with Ice Body heal 1/16 HP each turn

- Pokémon with Snow Cloak have 20% extra evasion

- Weather Ball becomes a 100 power Ice-type move

- Castform transforms to Hail Forme and becomes Ice-type

Fog

- All moves are 25% more likely to miss or fail

- Weather Ball becomes a 100 power Normal-type move

Shadow Sky (Move: Shadow Sky)

- All non-Shadow Pokémon take damage each turn

- Only appears in Pokémon Colosseum XD