I also see the +1 degree average temperature change from July to August, but I also see a 4 degree increase from June to July. Both months showed no change (44 minutes). 5 degrees seems like a significant rise in temperature, enough to increase the watering times. Plus I have to say, with global warming (and we feel it here), a 30 year average may no longer be accurate. It is currently 80 degrees (was 91 in my car on Wednesday) and has been so since the beginning of July.
June 71 degrees
July 75
August 76