That's true, but we had an unusually cold winter, so the 12-month period ending in August was the second coldest since 1998:
source: NOAA data for year-to-date since 1998; average line 1900-2010
Notice that U.S. temps have been declining for over a decade, and are only a bit above their 110-year average.
Luboš Motl of The Reference Frame calculates that there's only a 16 percent probability that 2010 will end up warmer than 1998. So it's too soon for certainty. But if the 5:1 odds don't pay off, Motl asks:
If 1998 remains the warmest year on record, you may wonder what is the appropriate global warming definition or the meaning of global warming that is consistent with the likely fact that 1998 will fail to be surpassed 12 times in a row.Previous post in the series here.