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Posted at 03:24 PM ET, 09/10/2012

Third hottest summer on record in Lower 48

Difference from average temperature across Lower 48 during the summer (June-August) (NOAA’s National Climatic Data Center)
The heat in August couldn’t match July’s record-smashing intensity across the continental U.S.. But the summer as a whole - spanning the entire June-August period - ranked 3rd hottest on record, NOAA reports today.

August ranked 16th warmest on record, with an average temperature 1.6 degrees above the 20th century average. Taking August together with the much warmer than average June (2 degrees above average, 14th warmest on record) and the singularly scorching July (3.3 degrees average), the entire summer averaged 2.3 degrees above average, trailing only 2011 (by 0.2 degrees) and 1936 (by 0.1 degrees) in the hottest summer rankings.

“The summer heatwaves this year were not quite as intense as the heat in 2011, but they affected more people,” writes Climate Central’s Andrew Freedman. “According to NOAA, more than 80 million people — about 10 million more than 2011 — experienced 100°F temperatures this summer.”

Percent of average precipitation in Lower 48 states during summer (June-August) (NOAA’s National Climatic Data Center)
The summer’s heat was closely linked to very dry conditions in the middle of the country. Writes NOAA’s Climate Watch Magazine:

Drier-than-average conditions prevailed across much of the central United States, from the Rocky Mountains to the Ohio Valley. Nebraska’s summer precipitation was almost 6 inches below average, and Wyoming’s precipitation was more than 2 inches below average, marking the driest summer on record for both states. Missouri, Illinois, Iowa, South Dakota, Nebraska, and New Mexico had summer precipitation totals among their ten driest.

At the end of August, more than two-thirds of the U.S. was experiencing moderate to exceptional drought. The hot, dry conditions stoked an active wildfire season. In August, more than 3.6 million acres burned nationwide, nearly twice average in the 12-year period of record.

Temperatures compared to normal for each calendar year through August dating back to 1895. The curve for 2012 (red) is much above the other warmest years (orange). (View big) (NOAA’s National Climatic Data Center)
While the summer heat didn’t quite pack 2011’s punch, the temperature this calendar year through August has been exceptionally warm in 117 years of record-keeping. It is a full degree above the next warmest year (1998), and some 4 degrees above average. (See above chart).

Warmest 12-month periods on record (1895 to present). The bars colored in red encompass 2012. (View big) (NOAA’s National Climatic Data Center)
The period spanning September 2011 through August was also unusually warm, ranking as the 4th warmest 12-month period on record. Amazingly, the five warmest 12-month periods have all ended in 2012. (See above chart)

By  |  03:24 PM ET, 09/10/2012

Categories:  Latest, U.S. Weather, Climate Change

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