Recent quotes:

In the winter of 1976-77, they point out, the temperature in Chicago stayed below freezing for 43 days straight, and in 1985 the city had a below-freezing stretch of 40 days. The longest stretch so far this winter was 11 days. Similarly, New York’s longest stretch below freezing this year has been six days, less than half as long as the freezing periods in the 1970s.Perhaps this is the real reason everyone is panicking about the cold: Winters have become so mild over the past 20 to 30 years that a blast of Arctic air feels extraordinary. “If you were 10 years old when this last happened and now you’re 40, that’s quite a chunk of your life,” Mr. Henson said.