As these graphs reveal, the latest NOAA temperature dataset, through August 31, 2013, confirms that the U.S. and its major crop regions are experiencing a cooling trend. (click on graphs to enlarge)
Note, this has taken place despite the largest 15-year production of human CO2 emissions, ever. Contrary to every single IPCC and U.S. climate model.
Update clarification: The above plots from the NOAA web site are based on moving 12-month periods ending in August (each 12-month period starts with a year's September temperature and ends with the following year's August temperature).
Additional modern, regional and historical temperature charts.