It is dry and cold in Jan in Chengdu, the average high temperature at daytime is 9C, and the average low temperature at night is 3C. You may pay attention to Chengdu weather(https://www.travelchinaguide.com/climate/chengdu.htm) to get real-time weather forecast later. It is cold to visit Leshan, but the daylight is much longer than 3 hours. There is a total of 56 buses from Chengdu to leshan directly daily, departin gfrom chengdu xinnanmen bus station, ximen bus station and chazidian bus station.