This video displays weather, and temperature systems.
Mapper can add func_precipitation to his map for better looks, and my mod has world and player core temperatures. So if map temperature decreases to 0 and bellow, the rain will become snow, and when it heats up above zero, snow will become rain again. Player body temperature also depends on weather temperature, in this video the body temperature is changing very fast, just to show how it looks.
Player body temperature decreases/increases depending on world temperature, also if player is in water for longer time he suffers hipothermia, body temperature also decreases when drinking water from spring, while it increases when you are near fire.
Also weather system will be more customizable, so maybe mapper will only have to add one entity and it might create lightnings, rain, snow and other effects, to seem like actual weather.
Even though the idea of the game is set in tropical island, but any server owner, that has it's own designed map can make it even on iceberg.
Last note. World temperature gradualy changes from 1 to 2 minutes from -1C to +1C, so it wouldn't always stay static, but theres an option to make it never go bellow/above 0 so it would always be correct background.