Can I wear T-shirt and Bermuda on the first week of November in Xi'an?

Well, it would be winter then. It may be cloudy and rain sometimes. The temeprature may range from 40F to 60F at that time. T-shirts and Bermuda won't be suitable.
You are advised to wear jackets, sweaters, shirts, and pants. Yes, you can enjoy multi coloured leaves then. :)

Thanks