You can use SetWeather or ForceWeather to change the weather to something you want, though it won't stick, as soon as you give AN a reason to take control, it'll set the weather it has down as being correct. It's fine for just testing out different weathers though.
Thank you, and found formid's I think......
370CE - Paradise
38EEC - overcast
38EED - snowing
38EEE - clear
38EEF - foggy
38EF0 - cloudy
38EF1 - thunderstorm
38EF2 - raining
836D5 - oblivion sky
I have these in a notepad file full of potentially useful formids, knew it would come in handy one day (though I ought to edit that to include console commands too)