Had the same problem. I found a fix, but with a tradeoff. Set all of these fog values to 1.0. This fixed it for me, but the tradeoff is you will be forced to put up with the white glowing trees, buildings, whatever is in the fog. When you turn these values all the way down, the fog goes away, but you still get a flicker and fog pop in which I believe is tied to the BS engine with FO4. [FOG] IgnoreWeatherSystem=true DistanceFadeDawn=1.0 DistanceFadeSunrise=1.0 DistanceFadeDay=1.0 DistanceFadeSunset=1.0 DistanceFadeDusk=1.0 DistanceFadeNight=1.0 DistanceFadeInteriorDay=1.0 DistanceFadeInteriorNight=1.0 VerticalFadeDawn=0.5 VerticalFadeSunrise=0.9 VerticalFadeDay=0.9 VerticalFadeSunset=0.9 VerticalFadeDusk=0.7 VerticalFadeNight=0.4 VerticalFadeInteriorDay=1.0 VerticalFadeInteriorNight=1.0