For the U.S., summer 2012 was third-hottest in history

According the National Climatic Data Center, summer 2012 was the third-warmest overall for the contiguous United States since record-keeping began in 1895. June 2012 was the 14th warmest June on record. July was the warmest month recorded (not just the warmest July) since record-keeping began in 1895. And August ended up being the 16th warmest August on record. Above-average temperatures have been the main story line for the contiguous United States for 2012. In fact, 2012 is the warmest on record for the year-to-date period of January – August. During the eight-month period, 33 states were record warm and an additional 12 states were top-10 warm. Meanwhile, the past 12 months (September 2011-August 2012) are the warmest 12 months ever recorded for the contiguous United States.

Weather events for August 2012. Image Credit: NCDC


August provided an average temperature of 74.4 degrees Fahrenheit, which was 1.6°F above the 20th century average, marking this August the 16th warmest August in a period of record that dates back to 1895. The Central U.S., Ohio Valley, and the U.S. Southeast regions of the contiguous United States experienced at or below-average temperatures for the month of August. According to the NCDC, 4,200 daily warm temperature records broken or tied during August, and just over 2,000 daily cool temperature records broken or tied.

In general, the western United States experienced hot and dry conditions that helped fuel wildfires throughout the region. Nearly 3.6 million acres burned nationwide, and acreage burned was nearly twice the August average and the most in the 12-year period of record.

The heat and low precipitation has pushed our average temperatures from June through August to become the third-hottest summer on record for the contiguous United States with an average temperature of 4.4°F, or 2.3°F above the 20th century average. Only the summers of 2011 (74.5°F) and 1936 (74.6°F) had higher temperatures for the Lower 48. Finally, September 2011-August 2012 period was the warmest such 12-month period on record for the contiguous U.S., with an average temperature of 56.0°F, 3.2°F above average.

June through August 2012 average temperatures in 2012 compared to normal. The extreme west coast and southeast United States experienced below-normal temperatures. Image Credit: NCDC/NOAA

When you look at the average temperatures for every August in the contiguous United States since record keeping began back in 1895, you can see a very obvious trend. The overall temperatures are slowly getting warmer throughout each decade. It is important never to focus on a particular region within the U.S. when it comes to looking at climate trends. You will see spikes of above and below average temperatures in parts of the Southeast/Pacific Northwest. Climate looks at a much bigger picture – such as the whole United States, or the entire Northern or Southern Hemisphere. In general, warming continues as the dominant climate story on Earth today.

Contiguous United States temperatures in Augusts that date back as far as 1895. Image Credit: NCDC/NOAA


Current drought across the United States. Hardest hit areas include the central United States and central Georgia. Image Credit: U.S. Drought Monitor

In August 2012, 55.1% of the contiguous U.S. was in moderate to extreme drought, a decrease of about 3% compared with July 2012. The percent area in severe-to-extreme drought increased to 39.0%, indicating that the drought has intensified. The 2012 values have been exceeded only by the droughts of the 1930s and 1950s. According to the September 4, 2012 Drought Monitor, 63.39% of the country is experiencing moderate to exceptional drought. Hurricane Isaac helped out portions of Arkansas, Illinois, Missouri, Tennessee, and Indiana with the drought, with many areas dropping from D3-D4 drought (extreme to exceptional) to D2-D3 drought levels (severe to extreme). Although these areas benefited from the extra rains, these areas could still use a lot more rain.

Bottom line: Summer 2012, which includes June, July, and August, was the third-hottest summer ever recorded since record keeping began in 1895. August was relatively cooler compared to July 2012, which is now the warmest month ever recorded. The past 12 months (September 2011-August 2012) are the warmest 12 months ever recorded for the contiguous United States. It will be interesting to see how we finish 2012. Could 2012 beat out 1998 as the warmest year ever recorded? Only time will tell.

September 11, 2012

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