Use the following entries with the fw or sw codes. If you add ,1 after the code (the weather override switch), the weather will stay like that until you either change it manually with fw or sw again, or you enable the code releaseweatheroverride.

Weather	Code
CamoranNatural	000370CE
Clear	00038EEE
Cloudy	00038EFE
Default	0000015E
Fog	00038EEF
OblivionStormTamriel	000836D5
OblivionStormTamrielMQ16	0006BC8B
Overcast	00038EEC
Rain	00038EF2
Snow	00038EED
Thunderstorm	00038EF1