Summer 2012: 3rd hottest in U.S. history

The summer of 2012 was the 3rd hottest summer in U.S. history, said NOAA's National Climatic Data Center (NCDC) in today's State of the Climate report. June 2012 ranked as the 14th warmest June on record, August was the 16th warmest August on record, and July was the warmest month of any month in U.S. history, bringing the average summer temperature of the contiguous U.S. just 0.2°F shy of the hottest summer on record--the great Dust Bowl summer of 1936. Second place is held by 2011, which was just 0.1°F cooler than the summer of 1936. So far in 2012, we've had the warmest March on record, 3rd warmest April, 2nd warmest May, and warmest July. These remarkably warm months have helped push temperatures in the contiguous U.S. to the warmest on record for the year-to-date period of January - August. Temperatures this year in the U.S. have been so far above the previous record--a remarkable 1°F for the year-to-date period--that even if the remainder of 2012 ranks historically in the coldest one-third of September - Decembers on record, 2012 will beat out 1998 for the warmest year in history. Reliable weather records for the U.S. go back to 1895. The most recent 12-month period of September 2011 - August 2012 was the 4th warmest 12-month period in U.S. history, exceeded only by the 12-month periods ending in July, June, and May of this year.


Figure 1. The summer of 2012 was the warmest on record for Wyoming and Colorado, and ranked in the top-ten warmest on record for 22 other states. For the Contiguous U.S., it was the 3rd warmest summer since record keeping began in 1895. Image credit: NOAA's National Climatic Data Center (NCDC).


Figure 2. Year-to-date temperatures for the contiguous U.S. through August, compared to the previous record warmest years in U.S. history. Outcome scenarios based on persistence of temperature from September through December, the remaining five months of 2012, are shown. Even if the remainder of 2012 ranks historically in the coldest one-third of September - Decembers on record, 2012 will beat out 1998 for the warmest year in history. The January-August 2012 contiguous U.S. average temperature was 58.7°F, 4.0°F above average. The data for 2012 are preliminary. Image credit: NOAA/NCDC.

Most extreme January - August period on record
The year-to-date period was the most extreme in U.S. history, according to NOAA's U.S. Climate Extremes Index (CEI), which tracks the percentage area of the contiguous U.S. experiencing top-10% and bottom-10% extremes in temperature, precipitation, and drought. The CEI was 47% during the year-to-date January - August period. This is the highest value since CEI record-keeping began in 1910, and more than double the average value of 20%. Remarkably, 85% of the contiguous U.S. had maximum temperatures that were in the warmest 10% historically during the first eight months of 2012, and 75% of the U.S. of the U.S. had warm minimum temperatures in the top 10%. The percentage area of the U.S. experiencing top-10% drought conditions was 22%, which was the 11th greatest since 1910.


Figure 3. NOAA's U.S. Climate Extremes Index (CEI) for January - August shows that 2012 had the most extreme first eight months of the year on record, with 47% of the contiguous U.S. experiencing top-10% extreme weather.

Jeff Masters