Sunny Day causes bright sunlight that lasts for 5 turns, and induces these additional effects:
- The power of Fire-type moves increases by 50%.
- The power of Water-type moves decreases by 50%.
- The accuracy of Thunder and Hurricane lowers to 50%.
- SolarBeam does not require the charging turn, thus attacks straight away.
- Pokemon with the ability Dry Skin lose 1⁄8 of their max HP each turn.
- Pokemon with the ability Chlorophyll double their speed.
- The move Weather Ball changes to Fire type and doubles in power.
- The moves Synthesis, Morning Sun and Moonlight recover 2⁄3 of the user's max HP (instead of the usual 1⁄2 HP).
- Castform changes to it's Sun Form