The year so far—January to August—now ranks as the warmest on record in the US, says NOAA's National Climatic Data Center.
The US Climate Extremes Index (USCEI) value for January-August was a record large 47 percent: more than twice the average value. Which beat the previous record of 46 percent set only last year. Extremes in warm daytime temperatures and warm nighttime temperatures contributed to the record high USCEI value.
As Wunderblog's Jeff Masters writes:
Temperatures this year in the US have been so far above the previous record... that even if the remainder of 2012 ranks historically in the coldest one-third of September-Decembers on record, 2012 will beat out 1998 for the warmest year in history. Reliable weather records for the US go back to 1895.
To put this in a global perspective, check out Kate Sheppard's posted video: The Warming World in Less Than 30 Seconds.