I'm going to Jordan in December/January. How cold does it get? I'm from Sydney if that helps with the answer.
I'm visiting Amman, Desert Castles, Jerash, Petra, Wadi Rum & Dead Sea
I travelled around Jordan last January and it did get quite cold at night in Amman, Wadi Rum and Petra, but no colder than a Sydney winter. However during the day it became very warm. My advice would be to take layers cause I think the temperature can vary a lot. The hostel owner in Petra (Valentine Inn - recommend it - great food) said that a few weeks earlier it had been snowing in Petra but when I went it was a bit chilly in the morning and at night but about 30 degrees during the day. Dead Sea will always be warm. Jordan is beautiful, have fun. If you have time get a shared taxi to Damascus too. Totally worth it. almost 10 years ago