Hot Summer Days

The average maximum temperature — the peak temperature on any given day — was well-above the 30-year average in many parts of the country during the summer of 2006. Between June and August 2006, the average maximum temperature was at least 0.5°F above the 30-year average at 169 (67%) of the stations we examined; 46 (18%) of these locations reported average summertime peak temperatures of at least 3°F above the 30-year average.

The Great Plains and Mountain West suffered some of the most above-normal peak summer temperatures in 2006. Rapid City, South Dakota and Sheridan, Wyoming both reported average peak temperatures of more than 6°F above the 30-year average during the summer of 2006. Seven other locations — including Oklahoma City, Oklahoma and Bismarck, North Dakota — experienced average maximum summertime temperatures of at least 5°F above normal (Table 3). See Appendix A for the average summertime peak temperature in 2006 for all weather stations.

The heat wave of 2006 not only raised average temperatures across the board, it resulted in many days where temperatures peaked at or above 90°F at locations across the country. Of the 235 weather stations we examined outside of Alaska,a 168 (71%) recorded a higher frequency of days in 2006 where the temperature reached at least 90°F, when compared with the historical average.b

Many locations experienced dozens more 90°F or warmer days than normal, particularly in the South and Southeast. In Mississippi, the Tupelo weather station recorded 103 days where the temperature hit at least 90°F in 2006 — 40 days more than the historical average. Similarly, Oklahoma City experienced 108 days where the temperature peaked at 90°F or higher, 40 days more than the historical average. Two locations in Texas — San Antonio and Austin — recorded 38 more days than normal with temperatures at or above 90°F (Table 4). See Appendix B for the frequency of 90°F or warmer days in 2006 for all weather stations.

a Alaska does not experience temperatures exceeding 90°F.

The "normal" annual frequency of 90°F or warmer days for each location is based on a varying number of years of climatological data. This ranges from 120 years of climatological data for Blue Hill, MA to 27 years of data for Redding, CA. The median number of years of climatological data used to compute the historical average is 44 years.

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