Cold Weather Will Grip U.S. Until Mid-January, Forecasters Say - BusinessWeek

Gas futures climbed to the highest intraday price since Dec. 9 following predictions that temperatures may be as much as 7 to 15 degrees Fahrenheit (minus 14 to minus 9 Celsius) below normal.
...
“In December, you had 30 of the 48 contiguous states below normal,” he said. “Now we are dealing with a pattern of 42 of 48 states being consistently below normal.”