Warmer-than-normal temperatures were anchored across the South, Mid-Atlantic and the Northeast. Delaware had its warmest year on record, while Texas had its second warmest year on record. The U.S. has observed a long-term temperature increase of about 0.12 degrees F per decade since 1895.

Summer (June-August) 2011 was the second warmest on record for the Lower 48, with an average temperature of 74.5 degrees F, just 0.1 degree F below the record-warm summer of 1936. The epicenter of the heat was the Southern Plains, where Louisiana, New Mexico, Oklahoma and Texas all had their warmest summer on record. The 3-month average temperatures for both Oklahoma (86.9 degrees F) and Texas (86.7 degrees F) surpassed the previous record for warmest summer in any state.

With the exception of Vermont, each state in the contiguous U.S. had at least one location that exceeded 100 degrees F. Summertime temperatures have increased across the U.S. at an average rate of 0.11 degrees F per decade. Much of this trend is due to increases in minimum temperatures (“overnight lows”), with minimum temperature extremes becoming increasingly commonplace in recent decades.