I was at Yellowknife in northern Canada. Temp was minus 30 something and dew point was the same. (F or C not an issue as minus 40 the same) Sky clear great day. Ground crew started the external power unit that was admittedly not up to current green standards. Much condensation and smoke ensued and the visibility went from unlimited to 50m in two minutes. We laughed and went for a coffee.
Yes Dew point and temp can be the same and in very cold air with no 'bits' in it (sorry forgot the pedants term) and - no prob - add the bits -whammee.
That technical enough?