From Sun to 7AU out I'm not sure about, but if you go far enough, the temperature of the emptiest of empty space is about 2.7 kelvin, i.e. 2.7 degrees above absolute zero (or at -270.3 degree celsius). This is the temperature associated with the cosmic microwave background radiation that pervades the entire universe.
See
http://map.gsfc.nasa.gov/m_uni/uni_101bbtest3.html
or
http://en.wikipedia.org/wiki/Cosmic_...ound_radiation (more detailed).