Sep 14
(from NOAA)
The 34th coolest summer (June-Aug) was below the long term average for US summers:
For the 2009 summer, the average temperature of 71.7 degrees F was 0.4 degree F below the 20th Century average. The 2008 average summer temperature was 72.7 degrees F
This matches my experience while traveling the nation this summer. We didn’t get sweaty and hot anywhere except a few days in Virginia.