Beijing weather in October

Hi Lucy.
According to the weather records of the past years, the average temeprature of Beijing was about 15 C. However, it is believed that it could be higher this October, at least about 20 C.
The mild sunshine and pleasant temperature would make October a good traveling time. So you can wear long-sleeved shirts then, of course, you can also take along an overcoat in case of the low temperature at night.