Wutaishan temperature in September and transport.

1. I have a trip to Wutaishan this September. What is the temperature at this time?

2. I also plan to stay overnight once at the East Peak and one night at the West Peak temples. Will it be very cold at night?

3. I checked the Chinese web for bus schedule from Taiyuan East Bus Station and it mentions that the last bus to leave for Wutaishan is at 3.30pm. But I saw replies from the travelchinaguide.com, the last bus is at 18:30. What is this differences?