It might still have a few rough edges - feel free to report any issues you find

Features

• Periodic rain cycles with configurable wet and dry durations
• Rain on multiple planets/surfaces, including Nauvis, Vulcanus, Fulgora, and modded planets (configurable)
• Rain can extinguish fires, with a configurable chance for each fire
• Pollution reduction during rain. Looks great with Pollution: Impactful Smog / Spore Cloud
• Reduced solar panel efficiency during rain (disabled by default)
• Lightning and thunder effects
• Configurable rain intensity
• Multiplayer support
• Commands to check the current weather or start a rain or dry period:
  /dynamic-rain status
/dynamic-rain rain
/dynamic-rain dry
/dynamic-rain lightning 0 0

Lightning strikes

Rare Fulgora-style lightning, but unlike on Fulgora, these strikes can instantly kill living creatures and ignite flammable structures, while leaving other structures undamaged. (Space Age only)

• Can kill players unless they are inside a vehicle
• Can kill enemies, spawners, drones, and fish
• Can ignite trees, fuel pipes (works best with Flammable Oils), wooden chests, and small wooden electric poles
• Electric poles take no damage but may temporarily stop conducting power
• Radars are temporarily disabled when struck
• Chain discharges are also dangerous
• Flying with Jetpack during a thunderstorm is extremely dangerous

Remote API

start_phase(...)

• Temporarily overrides the weather on the specified surface.
• If the requested phase is already active, resets its timer to duration_ticks. Otherwise, takes 600 ticks to fade rain in or out before starting the requested phase.
• After the duration ends, Dynamic Rain continues its own scheduler.
• Each call replaces all options. Omitted options use player settings.
• API-enabled surfaces remain enabled after the episode ends.

remote.call("dynamic-rain", "start_phase",
  surface_index, -- Existing surface index
  "wet",         -- "wet" or "dry"
  20000,         -- Duration: positive integer, ticks
  {              -- Optional; omitted fields use player settings
    intensity = 1,                       -- Absolute drop density: number >= 0 && < 100
    thunderstorm = false,                -- true / false; false disables thunder and lightning
    fire_extinguish_chance = 0.7,         -- 0..1; 0 disables extinguishing
    pollution_cleanup_per_minute = 10,   -- Number >= 0; 0 disables cleanup
    pollution_max_chunks_per_tick = 10   -- Positive integer
  }
)

To keep the surface dry until your next rain episode, call start_phase with "dry" and a suitable duration.

is_raining(...)

Returns true during the wet phase; false during dry weather or when rain is disabled.

local raining = remote.call("dynamic-rain", "is_raining", surface_index)

time_left(...)

Returns ticks remaining until the phase changes; 0 when rain is disabled.

local ticks_left = remote.call("dynamic-rain", "time_left", surface_index)

Events

local events = remote.call("dynamic-rain", "get_events")

script.on_event(events.on_phase_changed, function(event)
  -- Raised when the phase actually changes
  -- event.surface_index
  -- event.old_phase, event.phase: "wet" / "dry"
  -- event.duration_ticks: duration of the new phase
end)

script.on_event(events.on_rain_pollution_cleaned, function(event)
  -- Raised when rain removes pollution
  -- event.surface_index
  for _, chunk in ipairs(event.chunks) do
    -- chunk.chunk_position: { x, y }, chunk coordinates
    -- chunk.pollution_before: pollution before cleanup
    -- chunk.pollution_removed: amount removed
    -- chunk.pollution_after: pollution remaining
  end
end)