From Amman to Changsha, there are no direct flights but only connecting flights with one or two transfers. The connecting flights with one transfer is available on each Tue, Thu, and Saturday and the transfer place is at Hong Kong. From Hong Kong to Changsha, several flights are available daily. Yes, you need to apply for a visa in the China Embassy in Jordan. For the weather in Changsha, you could refer to the page: https://www.travelchinaguide.com/climate/changsha.htm