From National Climatic Data Center News
According to NOAA scientists, the average temperature for the contiguous U.S. for 2012 was 55.3°F, which was 3.2°F above the 20th century average and 1.0°F above the previous record from 1998. The year consisted of the fourth warmest winter, a record warm spring, the second warmest summer, and a warmer-than-average autumn. Although the last four months of 2012 did not bring the same unusual warmth as the first 8 months of the year, the September through December temperatures were warm enough for 2012 to remain the record warmest year, by a wide margin.
The average precipitation total for the contiguous U.S. for 2012 was 26.57 inches, 2.57 inches below average, and the 15th driest year on record for the nation.
The U.S. Climate Extremes Index indicated that 2012 was the second most extreme year on record for the nation. The index, which evaluates extremes in temperature and precipitation, as well as landfalling tropical cyclones, was nearly twice the average value and second only to 1998.
For more information:
http://www.ncdc.noaa.gov/news/ncdc-announces-warmest-year-record-contiguous-us