tour 16-24 April to Beijing, Xian, Shanghai - long sleeve shirt or short? long pants or shorts?

Edilberto, the average highest temperatures in these three cities are 20, 19 and 21 Celsius Degrees. So I think you should wear long sleeved shirts and long pants. If possible, bring a thin jacket in case it rains. At noon, you may wear shorts and short sleeved shirts.