September 2016 Summary – Seventh Warmest on Record

Blue Hill Observatory
September 2016 Summary:

The month continued the recent pattern of warmer and drier than average weather. The 24-hour mean temperature for the month of 65.2 deg F was 4.0 degrees warmer than the 120-year average for September and nearly three degrees warmer than the 1981-2010 30-year average. This made September the seventh warmest on record.  A daily high minimum temperature record of 71F was set on the 10th, which surpassed the previous record of 69F in three earlier years. The highest temperature for the month was 90F on the 9th, and the low temperature of 43F occurred on the 26th. There were 102 cooling degree days during September, which raised the seasonal total to 894. This is the second highest seasonal cooling degree day total since at least since 1960.  September brought only 2.35 inches of precipitation, which was more than an inch and a half inches less than the long-term 120-year average and the 30-year mean. The greatest amount in 24 hours was 1.06 inches on the 5th-6th. There were no days with thunderstorms during the month. The mean wind speed was 11.2 mph, with a prevailing direction from the south, and the peak gust was 42 mph from the north-northeast on the 5th. September sunshine was well below average with 51 percent of the possible bright sunshine being observed, which was six percent less than the long-term average.

BHO Warmest September 24-hour Mean Temperature, deg F (1885-2016):

1) 67.2 in 2015
2) 66.1 in 1961
3) 65.5 in 2005
4) 65.4 in 1999
  65.4 in 2010
6) 65.3 in 1930
7) 65.2 in 2016
8) 65.0 in 2002

BHO Greatest Number Seasonal Cooling Degree Days, (1960-2016):

1) 916 in 2010
2) 894 in 2016 (through September)
3) 811 in 2015
4) 805 in 1999
5) 780 in 2005

Mike Iacono
Chief Scientist
Blue Hill Observatory