Jiangnan? As we think, this is a big geographic area, meaning south of the Yangtze River. So, if this is not a specific place, which city do you mean by Jiangnan. Perhaps, some places are not as warm as 10-18 degrees. Guangzhou would be like this, not optimistic on Shanghai and Hangzhou. They are not very warm in winter. Not a peak season at that time, no school holidays.