Weren't they showing weather in videos months before the game came out? I assumed that those were regular tracks in those videos but I guess not.
I bought the game around release but shelved it after a week or so waiting for replays and weather.
Yes, you can setup rain or snow on any track in single race.
But in tour events it will only be included in upcoming DLC. Otherwise they would have to reset the leaderboards for the existing tour events in the main game.