Normal ain't what it used to be.

The National Climatic Data Center (NCDC) is responsible for producing 30 year climate normals for U.S. locations. As a result, the average temperature across the United States is now approximately 0.5 F degrees warmer than the 1971-2000 period. However, this warming is not uniform across the country or from season to season. For instance, the 1981-2010 average high temperature for the mid section of the U.S. is cooler in July compared to the previous set of normals. Meanwhile, the January normal lows are much warmer across the Northern Plains and Upper Mississippi River Valley compared to 1971-2000. The graphics below illustrate the changes, along with the overall warming by state from the old set of normals to the new set.