The National Oceanic and Atmospheric Administration's National Climatic Data Center reported today that the summer of 2012 "was the third hottest summer on record for the contiguous United States since recordkeeping began in 1895."
They looked at records from June through August of 2012 (summer is technically over on the morning of September 22).
...the average temperature for the contiguous United States between June and August was over 74° Fahrenheit, which is more than 2° F above the twentieth-century average. Only the summers of 2011 and 1936 have had higher summer temperatures for the Lower 48.
The online weather service, the Weather Underground, has compiled data that allows users to look at how their local climate has changed over the years.
It also allows users to see how local the climate is expected to change in the coming years using two different IPCC greenhouse gas emissions models.