Requires the world to be rectangular without missing maps, which is a problem for pupland.
Features and Ideas
Hooks in scripts (like the get_time, script should be able to use get_weather(object/map) to get temperature, humidity, etc). Imagine a powerfull sword that does not work below 5 Celcius :)
Weather dependent objects
Stuff that freezes and melts
Could make entrance into some maps interesting
Could possibly use same concept for dried out rivers and flaming pits (or something similar)
Instead of replacing objects, create various states that they may assume (regular, wet, snow, dry, etc)
leaves overlays to dms
allows for more objects to be affected by the weather