Data geeks at the National Oceanic and Atmospheric Administration (NOAA) took the reports of Record high temperatures across the country and plotted them on a map:

 The data map shows that record high temperatures were not confined to just one region:

How hot was the month of July in 2011? So hot that just by plotting the location of each daily heat record that was broken, a nearly complete image of the contiguous United States is visible. Almost 9,000 daily records were broken or tied last month, including 2,755 highest maximum temperatures and 6,171 highest minimum temperatures (i.e., nighttime records). It should be noted that the tally of records collected so far is not complete – more are expected to come in as station data from across the U.S. is mailed to the National Climatic Data Center. 

Hot weather in one location doesn't necessarily mean the entire earth is getting warmer. But the appearance of record highs in every region suggests that something unusual is going on.