Very impressive- high today was 13.5, currently it's 12.9. I believe that is record shattering cold.
Though - Christmas eve 1983 was a little colder during the afternoon hours than today was. I left work at 5pm and it was 3 degrees after being in the upper 20s earlier in the morning.
Both air masses were/are historic, though the 1983 outbreak featured subzero temps here that this outbreak will not.