How does weather work in UO?

Is it on a timer, random, some other means? Is there any way to forecast when it will rain or snow?

It's mainly random, based on some set values for the temp, chance of precipitation, weather temp, etc.

You can change the weather yourself using Razor..

Types
0 - "It starts to rain"
1 - "A fierce storm approaches."
2 - "It begins to snow"
3 - "A storm is brewing."
255 - None (turns off sound effects)

ie: This would make it rain a little

And this would main it rain a lot

Good info. Thank you, Quick.