Smog or no smog, it's quite rare to actually see the sun out in Chengdu. It's always misty and overcast, which add to the air quality problem. Last winter, I unwittingly left the window of my hotel room open overnight (because it was quite pleasant, about 60F/17?C). I ended up waking up in the middle of sleep with a cough, something that had not happened to me by my best recollection.

The Panda Research Base is within city limits, but it's quite time consuming to get there and back because of the snarling traffic. I got there first thing in the morning, setting out before sunrise. I thought it was well worth the effort, because panda feeding time is around 8 or 9 am (check the website). They are active until about 10 am, and then fall fast asleep by the time the crowds arrive by tour bus.