Sunday, July 22, 2012

32nd Consecutive Warm Week Puts U.S. on Track for Record Hottest Month

July 24 Update: The National Climatic Data Center preliminary monthly average temperature through July 21, posted today, is 77.6°, which is still 0.2° above the previous record.

Original Post:
With 10 days left in July, the 32nd consecutive week of warmer than average temperatures has put the U.S. on track for the hottest month since national temperature records began in 1895. CapitalClimate analysis of National Weather Service reports from 215 stations across the 48 contiguous states shows that the unadjusted U.S. national average temperature was 3.6° above climatological normal for the week ending yesterday, July 21, up from 2.9° last week. With the National Climatic Data Center adjusted month-to-date average of 77.9° through July 14, it is now likely that the July average through the first 3 weeks of the month will exceed the all-time hottest U.S. month of July 1936 at 77.4°.

This is not a prediction, but if present trends continue, July 2012 would become the new record hottest month. If this does occur, 2 out of the 5 hottest months will have occurred within the last 2 years, and 3 out of the 5 will have occurred within the last 7 years (July 2006 being the third). Note that all of the hottest months shown in the chart at the top are July; the hottest August on record was 75.8° in 1983.

The charts to the right show the current month-to-date average temperatures through July 21 and the July 1936 monthly average. The numerical scales are equivalent, but the color schemes are not identical. In particular, the white area for 1936 corresponds to both yellow and light green for 2012.

Images (click to enlarge):
- Hottest U.S. average monthly temperatures (all July) and 2012 average through July 14; CapitalClimate chart from NOAA/NCDC data
- Weekly average U.S. temperature departures from normal, weeks ending June 4, 2011 (20110604) through July 21, 2012 (20120721); CapitalClimate chart from NOAA/NCDC data
- Average U.S. temperature departure from normal for July 1-21, 2012 from High Plains Regional Climate Center
- Average U.S. temperature departure from normal for July 1936 from NOAA/ESRL

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