Summer of Simmer: August Week 1 Update

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Following a slight break on Saturday (high 87°, low 68°), Washington, DC's summer was back on simmer by yesterday with a high temperature of 91°. After readings of 92° for 4 consecutive hours, it was likely that today's high would be warmer than that, and in fact the maximum so far is 93°. Meanwhile, the low so far of 75° is 5° above the forecast, and that is likely to hold through midnight.

The cumulative average temperature so far this summer is now a toasty 81.7° for the 70 days of meteorological summer since June 1. This is 4.6° above the 30-year climatological average and an incredible 2° or more above each of the 3 previous hottest summers to date. There has never been a summer in Washington with an average temperature above 80°, but with August so far averaging 80.7°, all 3 months this summer are above 80°.

Using the National Weather Service forecast temperatures for the next 7 days and climatological averages for the rest of the month, the summer of 2010 would average 80.9°, nearly a whole degree above the old record in 1980. However, the extended outlook from the Climate Prediction Center calls for over a 60% chance of above-normal temperatures for August 15-19 and a 50-60% chance of above-normal for August 17-23. If this pans out, the final average could very well be higher.

Images (click to enlarge): Washington, DC average summer temperatures to date for 2010 and previous record years 1980, 1991, 2002, and climatological period 1971-2000; Daily high temperatures, summer 2010 (portion above 90° in dark red); CapitalClimate charts from National Weather Service data, background photo from Kevin Ambrose; 6-10 day and 8-14 day temperature outlooks from Climate Prediction Center/NWS