Hi,lilianoty!
You are very welcome to contact me and meet for a coffee (or 2).
December is pretty cold in Iceland, but as most of lifetime it´s spent indoors,then you´ll see a nice winter landscape,from a wonderfully warm buiding.
You should bring a good and warm jacket/coat. Everywhere you´ll go (indoors),it will be warm and cozy, since in Iceland,the heating is very cheap and good, so you have to worry just for being warm between the car/bus and the place you have to go.
Send me a private message telling me if you plan to travel around and where in Iceland you´ll be,and i´ll try to help you better.
Looking forward!
Olga ^_^