Temperature is propotional to the average kinetic energy of an idealized mon-atomic gas. So if in space there is some energy, there will be some temperature. Just a few nano Kelvin above absolute zero.
If talking about virtual particles with properties like inverse time travel, negative mass or what ever is needed to get the dimensions right for the result to make sense, I do not see any sensible way of assigning a real (as opposed to the imaginary part) value to something completely imaginary/virtual. That virtual temperature could be well below the absolute 0 temperature