Quote: --- Original message by: UnevenElefant5
To make weather you need to find the .weather_particle_system tag which can be extracted from the campaign maps.

For rain I modified the c10 one to remove the insects. Snow you can get from c40 I believe.
They should be in tags\levels\levelname\

Then edit as you wish.
Now, in sapien, go to cluster properties -> palettes -> weather palette

Then click "New Instance" at the top.
select your new instance and reference the particle system. Set scale function to 1
Then reference the wind. (If you don't the flags wont wave in the wind)
A decent .wind tag can be found in tags\levels\b30\outside.wind

Set the direction to X: 1 Y: 1 Z: 1 the magnitude to 1 as well as the scale function.
Then Ctrl + S to save it. Make sure you save it immediately afterwards, because you are modifying the BSP not the .scenario, if you click on something like "vehicles" it will save the scenario, but if you have anything under "cluster properties" selected it will save the bsp.