Beijing in the winter, prevent cold shock and travelling lightly

Hi there, I plan to go to BJ end of Dec till early Jan (5 days). I'm from a tropical country (though I have lived in cold countries previously but i'm sure the cold will be quite a shock for me), any advice on how I could travel as light as possible yet effectively? (can't imaging fitting thick woolen sweaters and down jackets in my backpack). I'll also be spending new years there, (i know that it's not really celebrated there), any advice on where I could visit without it being a club-party? thanks a bunch!