I got the weather thing working in the PC version, but the scripting in the Xbox sems to be different. Because it doesn't work.
I just created a new "container" type of item and gave it the following script, using the function ModRegion to change the weather:
begin LA_weather_scroll
if( OnActivate )
ModRegion, "Bitter Coast Region", 0, 0, 0, 0, 100, 0, 0, 0, 0, 0
MessageBox "Changed weather to Rain in Bitter Coast Region"
endif
end
After saving it in a new .esp. I tested it in the PC version of Morrowind. It worked like a charm. As soon as I activated it, the weather began to change slowly, and it started raining. And since I gave it a 100% chance of rain, it is supposed to rain in the Bitter Coast Region forever.
I used TESDK to apply the Xbox Morrowind.esm dependency, and saved it. Transferred it to the Xbox, but it didn't work. If you activated the paper nothing would happen. At that point the sky was clear in Seyda Neen (the town I used to test, since it is in the Bitter Coast region) and I waited over 3 minutes and nothing happened.
I guess the scripting for the Xbox works differently.
If anyone can shed some light in these, they are welcome.