This comment was written in the above part of my script:
-- Snow manager script.
-- Author: Diarandor (Solarus Team).
-- License: GPL v3-or-later.
-- Donations: solarus-games.org, diarandor at gmail dot com.
--[[ Instructions:
To add this script to your game, call from game_manager script:
require("scripts/weather/snow_manager")
The functions here defined are:
game:get_snow_mode()
game:set_snow_mode(snow_mode)
game:get_world_snow_mode(world)
game:set_world_snow_mode(world, snow_mode)
snow modes: "snow", "snowstorm", nil (no snow).
Warning: all events registered below with the syntax of the multi_events script
need to be "registered" in the same way in other scripts, if defined, to avoid overriding
previous code. Otherwise, you will get errors and the script will not work as it should.
--]]
I hope that answers your question.