That 1917-18 week set a lot of records. NYC had temps of 8/-6, 2/-13, 6/-7, 10/-4, 10/2, 12/0, 18/-3. Week average: 9.4/-4.4/2.5
A century later (and a lot farther north) we bridged into the new year with 6/-16, -3/-14, -1/-31, 7/-25, 1/-18, 1/-24, 6/-27 Week average: 2.4/-22.1/-10.9