That could be a cool idea for a new Fallout game. A “Prehistoric” world but with landmarks EVEN more destroyed. Like the movie “Planet of the Apes”

One is an absolute fact. The other.....isn't.

True, Nuclear Winter is only assumed to be a side effect.

It's one of those things you can't really test for without killing a few billion.

^ No bro. I meant nuclear winter IS the absolute fact

If you think about Fallout could have happened in the real world. As the USA sent a false missile alert to a Small Russian base and there was a man named Stanislav Petrov, who knew it was a false threat and saved humanity. See Perry the Platypus I know my World History, except that I DONT

And also a a great Youtuber (Emplemon) made a video called “There may never be a man as strong as Stanislav Petrov” he explained it much better than I ever could.

I guess I always assumed the early Mad Max movies were set in the Australian Outback, which is a desert now rather than a result of nuclear armageddon.

Nuclear Winter is what would happen, in the long term places might end up becoming deserts because vegetation and wildlife are wiped out.

Well, deserts exist already, and if the world ends, then they will be post apocalyptic deserts. Nuclear weapons are not going to cause jungles to sprout up overnight in any of these arid locations, be it the Mojave, the Gobi, or what have you. So by default, these deserts are guaranteed to be post apocalyptic and will be so the very second the world "ends." A nuclear winter might occur, but an eventually is slower on the draw than instantaneously.

Well realistically speaking the weather wouldn't even matter, as if the same volume of bombs as the ones in Fallout dropped in our world the radioactive fallout alone would probably kill most if not all animal life, even if they survived the initial explosion.

But to answer your question I think a nuclear winter would be the most likely as all the fallout and general guff from the bombs would probably block the sun for a good while, lowering the temperature in a way a bit similar to a volcano eruption. But I could just be talking out my ass

Both probably. Cold climates actually reduce overall precipitation, so we will see the expansion of deserts.

However, human activity is already causing desertification. The interuption of harmful agricultural practices, land clearing, and over grazing could allow areas to recover. But the ecological damage will also disrupt ecosystems, possibly creating more deserts.