September 2019 Summary – Warmer, Drier and Sunnier Than Average

Blue Hill Observatory September 2019 Summary:

September was generally warm and sunny with much less rainfall than average. The 24-hour adjusted mean temperature for the month of 63.4 deg F was 2.2 degrees warmer than the 120-year average for September and 1.3 degrees warmer than the 1981-2010 30-year average. The average maximum temperature of 73.6 deg F was 2.0 degrees above normal, and the average minimum temperature of 54.5 deg F was 0.1 degrees below normal. The warmest temperature for the month was 88F on the 23rd, and the lowest temperature was 43F on the 19th. Precipitation totaled 1.27 inches, which was nearly three inches less than the long-term 120-year average and more than two and a half inches less than the 30-year mean. Most of the monthly rainfall fell on just five days, and the greatest precipitation in 24 hours was only 0.37 inches on the 2nd. There were no thunderstorm days during September. The mean wind speed was 10.9 mph, and the prevailing wind direction for the month was from the south-southwest. A peak gust of 39 mph from the west occurred during the rainfall on the 2nd. September provided abundant sunshine with 246.5 hours of bright sunshine, or 69 percent of possible, and September ranked as the 10th sunniest on record.

BHO Sunniest Septembers, hours (1886-2019):

1) 267.7 in 1983 [74%] 2) 266.9 in 1941 [74%] 3) 265.9 in 2007 [74%] 4) 255.3 in 1948 [71%] 5) 251.9 in 2015 [70%] 6) 251.0 in 1967 [70%] 7) 246.8 in 1952 [69%]    246.8 in 1978 [69%] 9) 246.7 in 1953 [69%] 10) 246.5 in 2019 [69%]

Mike Iacono
Chief Scientist
Blue Hill Observatory