If you load Railgun or Radar, do the atmospheric effects work? It could be a disabled cvar, cg_atmosphericEffects IIRC.
If they do, please post the Trace Map 
And perhaps the sky shader.
If you load Railgun or Radar, do the atmospheric effects work? It could be a disabled cvar, cg_atmosphericEffects IIRC.
If they do, please post the Trace Map And perhaps the sky shader.