Which completely destroyed the dry air theory which stated that the dry air with no rain that surrounds capitol wasteland preserves many of those scorched wooden ruins and this theory is the only "logical" answer to the "200 years and scorched houses still standing? ridiculous!" question...
Yes actually it would destroy that theory.
Bottom line is that Human beings posses no capability of stopping the rain, even if ALL the bombs fell. The laws of physics still apply, water still evaporates and goes up, forming clouds. Clouds move around from the wind, and drop rain. The wind comes from the global climate cycle, which isn't going to change no matter what happens or what we do unless the planet freezes into a Snowball Earth or spirals into the Sun (which might be interesting actually). So yes, from a science-based perspective, there would be no stopping the rain. And with that, no stopping the re-greening of the world. From my view, the actual DC Wasteland 200+ years after the war would not only be green, but filled with trees, new growth and the inevitable re-claiming of the land from us by nature. However, if they simply changed the dates around so that Fo3 takes place say 10-20 years after the war, then the wasteland does resemble what a scorched landscape would look like - but there would still be rain.
That said, having a Green world filled with trees and rain wouldn't create as much the feeling of immersion that one gets when walking through a true Wasteland, and I give massive credit to Bethesda for keeping the game's goals and themes primary over realism (and realism can ruin a game if applied too thickly). Still I think it would have been Dynamite to have radioactive rain - rain that forces players in-doors or burns their Rad-X/RadAway supplies - that would have been cool. As it is, I love the game's immersion and atmosphere - I just added Rain/Weather/Greenery via the Mods and get exactly what I envision it might be like.
Miax