Statewide changes in annual “normal temperatures” (1981 - 2010 compared to 1971 - 2000). (NOAA) On July 1, NOAA will release its new climate normals, which serve as the basis for comparing current weather to recent history. For the past decade, the climate normals spanned 1971-2000. The new climate normals cover the period 1981-2010. And these new normals are warmer than the normals of the past. Over the United States, they have warmed 0.5 degrees F between the two periods.

“The climate of the 2000s is about 1.5 degree F warmer than the 1970s, so we would expect the updated 30-year normals to be warmer,” said Thomas R. Karl, director of the National Climatic Data Center.

According to NOAA, the “normal” annual maximum and minimum temperature increased in every state across the contiguous United States (as shown in the figure above).

Changes in normal temps from 1971-2000 period to 1981-2010 period for maximum temperatures in January and July over the U.S. Darket red shade indicates warming of 2-4 deg F. Darkest blue shade indicates a cooling of 1-1.5 deg F. (NOAA National Climatic Data Center) While warming has occurred in all seasons, winter temperatures have warmed much more rapidly than summer as shown in the graphic above.

In addition to updating time period for the normals, NOAA undertook quality control measures to improve methodology for computing them. Details about these improvements can be found in a briefing on the changes.