This command sets the weather (non-forcefully) to the specified weather type. The weather will likely change to a different type naturally soon after.
setweather [weather id]
| Weather ID | The ID of the weather type you wish to set the weather in the game to. See weather IDs. |
SetWeather 0007548F
The above command would set the weather to sunlight (sunlight has a weather ID of 0007548F).