With this script you can control the weather easily...
Write in the console ("Ñ" by default) one of the next commands:
Cloudy
Drizzle
ExtraSunny
ExtraSunny2
Foggy
Rainy
Sunny
SunnyWindy
SunnyWindy2
ThunderStorm
If you write a command correctly, after 1 second, the game will display a text telling you "Weather Changed"...
It´s not 100% effectively, and it takes some minutes to take effect, but it´s better than nothing ...