Shanghai in winter can be bad - ie, just below freezing, snow&rain mix, and just miserable, or it can be fairly pleasant, read above 10C, sunny..

It depends heavily on the day..

I also agree with others that some months in spring/autumn it's almost guaranteed to be nice weather (15-25C) while in summer it's just too hot (albeit, I enjoy a hot day, the difference of strong AC inside and hot weather outside is really brutal)

So if you're used to winter, it won't be that bad.. as others said, bring accordingly, and if you're lucky, you're in for some mild, fresh weather with good air..

If you're unlucky, it's snow&rain, wet and humid..