What we see here is this past early winter, with 36 days of lows of 20 below or lower before New Years Day, was the third highest total since 1930. The red line represents the 5-year running median, which is now back up to values common in the mid 1990s and during the past negative PDO phase (transitions between phases marked by the black lines). The plot of lowest absolute temperature during early winter does not paint the same picture:
This clearly shows that absolute low temperatures have been increasing. Prior to 1980, temperatures of 50 below or lower did not occur every early winter, but were by no means uncommon. Since 1980…just one year, 1999. This however must, in part, be attributable to increase in urban effect, which is greatly amplified by the formation of ice fog at temperatures colder than -35F.