User blog comment:Master Sima Yi/Assassinews 04-06-'12 — E3 hub/@comment-115.186.172.53-20120607115211/@comment-5254145-20120607180152

I would assume that throughout the story the seasons will change accordingly to the time, but I hope at the end it will change after a certain amount of time. So you can still free roam in all weather even after completion of the game.