A theory of the 1980's, whether or not it was founded or not, determined that if a nuclear war occurred, the sheer and unmitigated number of detonations and the power of those nuclear reactions would alter the tilt of the Earth. When El Nino and El Nana ocured, the planet shifted it's tilt a mere 0.5 of a degree, and the problems it caused in climate and global water flows was very noticeable, and the number of deaths in aquatic life alone was more than noticeable. Likewise, the sun's rays hit the earth at a different parallel, and as we all know, the sun is the driving force for our entire planet's eco systems, being that it is the principal source of energy for our world. But when the El Nino and El Nana effect occur, they occur once every 500 years.

Take into account the nuclear fallout of the Great War. The massive levels of EMP eruptions that happen just prior to nucelar strike and then compound that by hundreds of times, adding the sheer amount of dust thrown up into the air, then the electromagnetic release messes with our electromagnetic flow of our planet, and the world goes through a correction process.

As such, notice that the Capitol Wastelands had an environment that'd remind you of maybe California or Mexico. In present day, the Washington area is near to a "Rainforest" area (a band that stretches across America from Maine to Washington State for example), and the region is supposed to be very fertile. True, the nuclear damage would've cooked off a lot of that, but I believe that in 200 years that most of that should've grown back at least in part. My theory to explain this is that the Earth has been tilted on its axis at an odd angle, transforming the intensity of the sunlight on certain areas while likewise thrusting areas like Canada, London, Norway and Russia a lot closer to what would now be considered the new north pole, while at the same time shunting areas like the Capitol wasteland into conditions resembling present day Mexico, parts of Texas or southern California.

What this necessitates is that Canada gets to be the new northern rainforest area, and prosperity for human life becomes easier for us there. Hence why Ronto (Toronto?) prospers so well, because they were a low military target, have resources, farm land, falling water and lots of water sources, not to mention a lot of pre-war tech.

What do you all think? I mean I don't have much to back up this theory, but it would explain a lot about how the climates change in the world.

As being a native Californian near the mexican border, I can say its nothing even remotely close.

The wasteland is dead. That is all. There are clear indications that the area used to be forested.