Weather and terrain in Pokémon Champions

What is known

• With its rock

  A Pokémon holding the weather's rock makes the weather it sets last 8 turns.

  • SunHeat Rock
  • RainDamp Rock
  • SandSmooth Rock
  • SnowIcy Rock

  Unknown in the mechanics ledgerEngine (Showdown’s mod)read Nov 2

  Details

  • Sources
    • Engine (Showdown’s mod) Showdown's Champions mod: weather duration, 8 turns with the setter's rock
  • What DexDB doesNot modelled in the calc, which does not count turns; the sim runs the engine's rule
  • NoteNo game count: the engine's rule is what DexDB plays.
  • ReadNov 2, 2026
• Setter leaves

  Weather from an ability runs its 5 turns from when it was set, even if its setter leaves. Only primal weathers end on leaving, and they are not legal.

  Unknown in the mechanics ledgerEngine (Showdown’s mod)read Nov 2

  Details

  • Sources
    • Engine (Showdown’s mod) DexDB ran the engine with a Drizzle lead that left: the rain was gone at turn 6 only
  • What DexDB doesPartly: matches for weather you set by hand; for ability weather the calc drops it with its bringer (fix queued)
  • NoteOfficial pages do not state it. No game count: the engine's rule is what DexDB plays.
  • ReadNov 2, 2026
• Mega into the same weather

  A Mega Evolving into the weather already up does not refresh it.

  Unknown in the mechanics ledgerEngine (Showdown’s mod)read Nov 1

  Details

  • Sources
    • Engine (Showdown’s mod) DexDB ran the engine: Mega Charizard Y into sun already up counted down 5, 4, 3, 2, 1, then it ended
  • What DexDB doesNot modelled in the calc; the sim runs the engine's rule
  • ReadNov 1, 2026
• Who sets it

  Mega Charizard Y brings sun, Mega Tyranitar sand, Mega Abomasnow and Mega Froslass snow, Mega Raichu X Electric Terrain. None brings rain.

  Unknown in the mechanics ledgerEngine (Showdown’s mod)read Nov 1

  Details

  • Sources
    • Engine (Showdown’s mod) DexDB read the engine's Pokémon data for every Mega
  • What DexDB doesModelled: the calc sets weather from the ability's name
  • ReadNov 1, 2026
• Cloud Nine

  Weather keeps counting down while Cloud Nine switches its effects off.

  Unknown in the mechanics ledgerEngine (Showdown’s mod)read Nov 1

  Details

  • Sources
    • Engine (Showdown’s mod) Showdown's Champions mod: weather returns when Cloud Nine leaves
  • What DexDB doesPartly: the calc switches the effects off; it does not count turns
  • ReadNov 1, 2026
• Mega Sol

  A Pokémon with Mega Sol hits with Water moves as if the sun were up: halved.

  Reported in the mechanics ledgerA player’s countA reportEngine (Showdown’s mod)as of Apr 17

  Details

  • Sources
    • A player’s count Smogon research thread #170: Mega Sol moved by Skill Swap: a Water move (Aqua Jet) did 12 against an expected 19 to 24 (dhelmise) Apr 17, 2026
    • A report Smogon research thread, the opening list: the holder has its Water moves weakened, no count
    • Engine (Showdown’s mod) Showdown's Champions mod: Mega Sol
  • CountOne hit: 12 damage against an expected 19 to 24
  • What DexDB doesModelled: @smogon/calc applies it
  • Note#170 tests Water only. Fire x1.5 rests on the engine alone (see the Fire row).
  • ReadNov 2, 2026

  A Pokémon with Mega Sol hits with Fire moves at x1.5, as in sun.

  Unknown in the mechanics ledgerEngine (Showdown’s mod)read Nov 2

  Details

  • Sources
    • Engine (Showdown’s mod) Showdown's Champions mod: Mega Sol
  • What DexDB doesModelled: @smogon/calc applies it
  • NoteThe opening list names only the Water penalty, and #170 tested Water. No game count: the engine's rule is what DexDB plays.
  • ReadNov 2, 2026

  A Pokémon holding Mega Sol keeps its own Sand or Snow defence boost when it is hit.

  Reported in the mechanics ledgerA player’s countEngine (Showdown’s mod)as of Apr 17

  Details

  • Sources
    • A player’s count Smogon research thread #170: Alolan Ninetales with Mega Sol in snow lost 16 to Aqua Jet, inside the snow range of 16 to 19 (dhelmise) Apr 17, 2026
    • Engine (Showdown’s mod) Showdown's Champions mod: Mega Sol
  • CountOne hit in Snow: 16 damage, inside 16 to 19
  • What DexDB doesModelled: @smogon/calc keeps the boost
  • NoteThe post says Sand works the same but gives no numbers for it.
  • ReadNov 2, 2026

  A Pokémon with Mega Sol attacking ignores the target's Sand or Snow defence boost. No clean test exists.

  Reported in the mechanics ledgerA reportEngine (Showdown’s mod)as of Apr 10

  Details

  • Sources
    • A report Smogon research thread, the opening list: the user ignores the target's Sand or Snow boost, no count
    • A report Smogon research thread #121: a friend's test relayed by a poster, no numbers; #123 says the target was the ally of the Cloud Nine Pokémon; #124 points out Cloud Nine suppresses the boost already Apr 10, 2026
    • Engine (Showdown’s mod) Showdown's Champions mod: Mega Sol
  • What DexDB doesModelled: @smogon/calc drops the boost; the board does not yet say it was never cleanly tested
  • NoteThe one test had Cloud Nine up, which already switches the boost off. Nothing else shows the holder case.
  • ReadNov 2, 2026

  With Mega Sol, Thunder and Hurricane have 50% accuracy.

  Reported in the mechanics ledgerA player’s countEngine (Showdown’s mod)as of Apr 18

  Details

  • Sources
    • A player’s count Smogon research thread #174: 20 of 50 hits, relayed from an unnamed Reddit user (older build) Apr 18, 2026
    • Engine (Showdown’s mod) Showdown's Champions mod: Mega Sol
  • Count20 hits in 50 tries
  • What DexDB doesPartly: the sim runs the engine's 50%; the calc's accuracy misses it
  • ReadNov 2, 2026

  Electro Shot still takes a charge turn for a Pokémon with Mega Sol, even in rain.

  Reported in the mechanics ledgerA reportEngine (Showdown’s mod)as of Sep 19

  Details

  • Sources
    • A report Smogon research thread #244: report, no sample linked (Hydrametr0nice) Sep 19, 2026
    • Engine (Showdown’s mod) Showdown's Champions mod: Mega Sol
  • What DexDB doesNot modelled in the calc fight, which follows the weather bar; the sim runs the engine's rule
  • ReadNov 2, 2026

  Growth raises Attack and Sp. Atk by 2 for a Pokémon with Mega Sol.

  Reported in the mechanics ledgerA reportEngine (Showdown’s mod)as of Sep 7

  Details

  • Sources
    • A report Smogon research thread #226: report that it's fixed, no sample Sep 7, 2026
    • Engine (Showdown’s mod) Showdown's Champions mod: Mega Sol
  • What DexDB doesNot modelled in the calc fight, which follows the weather bar; the sim runs the engine's rule
  • NoteEarlier the other way: the opening post listed Growth failing under Mega Sol as a suspected bug, and #174 (Apr 18, relayed from Reddit) said it fails unless harsh sunlight is already up. #226 (Sep 7) says it was fixed.
  • ReadNov 2, 2026
• Terrains

  A terrain lasts 5 turns, 8 with Terrain Extender, and only affects grounded Pokémon.

  Unknown in the mechanics ledgerEngine (Showdown’s mod)read Nov 1

  Details

  • Sources
    • Engine (Showdown’s mod) Showdown's Champions mod: terrain duration
  • What DexDB doesPartly: the sim runs the engine's count; the calc holds a terrain until you change it
  • ReadNov 1, 2026

Each statement is a row of the mechanics ledger, with its sources. Unknown means no game evidence, so DexDB plays the engine’s rule.

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