November 2021 Summary – Sunniest on Record

Blue Hill Observatory November 2021 Summary: 

November was near average for temperature and much drier than average. The 24-hour adjusted mean temperature for the month of 41.6 deg F was 0.9 degrees warmer than the 1891-2020 130-year average for November, and it was 0.5 degrees cooler than the 1991-2020 30-year average. The average maximum temperature of 50.8 deg F was 1.9 degrees warmer than the 130-year mean. The average minimum temperature of 33.6 deg F was 0.2 degrees cooler than the 130-year mean. The highest temperature observed all month was 69F on the 18th, and the lowest temperature during November was 21F on the 30th. The first freeze of the season of 31F was recorded on the 4th, which was relatively late compared to the average date of October 20th, and it was the latest first freeze since 31F on November 9th, 2017. The total precipitation was 1.92 inches, which was nearly two and a half inches less than the 130-year average and the 1991-2020 30-year mean. More than half of this rainfall, 1.00 inches, occurred in less than twelve hours on the 12th during a period of very strong winds, and this precipitation was also the greatest rainfall in 24 hours during the month. There was one thunderstorm days during November on the 13th, which raises the annual total to 25. The first measurable snow of the season was observed during the night of the 26th-27th, when 1.0 inches was measured. This was also the total for the month and the greatest snowfall in 24 hours for November. The mean wind speed for the month was 11.7 mph, which was the lowest on record for November, and the prevailing wind direction was from the west-northwest. The highest wind gust was 72 mph from the SSE during the heavy rain on the 12th. November sunshine was the highest on record for the month with 191.1 hours, which was 67 percent of the possible bright sunshine and 19 percent more than the long-term average. 

BHO Lowest November Mean Wind Speed, mph (1885-2021):

1) 11.7 in 2021
2) 11.9 in 2016
3) 12.1 in 1992
   12.1 in 2000
5) 12.3 in 2012

BHO Highest November Sunshine, hours (1886-2021):

1) 191.1 in 2021 [67%]
2) 182.3 in 1939 [64%]
3) 181.5 in 1917 [64%]
4) 181.4 in 1976 [64%]
5) 173.9 in 1905 [61%]

Blue Hill Observatory Fall (September – November) 2021 Summary:

Fall was much warmer and much wetter than average. The 24-hour adjusted mean temperature for the season of 54.2 deg F was 3.1 degrees warmer than the 1891-2020 130-year average for Fall, and it was 1.7 degrees warmer than the 1991-2020 30-year average. The average maximum temperature of 62.7 deg F was 2.5 degrees warmer than the 130-year mean. The average minimum temperature of 46.8 deg F was 3.1 degrees warmer than the 130-year mean, and it was the fourth warmest on record. The temperature extremes during Fall ranged from a high of 82F on September 15th to a low of 21F on November 30th The total seasonal precipitation was 16.43 inches, which was four inches more than the 130-year average and two and a half inches more the 1991-2020 30-year mean. Most of this rainfall occurred in September and October, including 4.00 inches from the remains of Hurricane Ida in early September and three heavy rainfall events in October. There were four thunderstorm days during Fall, which was one more than average. The mean wind speed for the season was 11.4 mph, which was the lowest on record, and the prevailing wind direction was from the west-northwest. The highest wind gust was 72 mph from the SSEE during heavy rain on November 12th. Although September and October were wetter and cloudier than average, a relatively dry and record sunny November compensated so that Fall sunshine was above average with 57 percent of the possible bright sunshine, which was three percent more than the long-term average. 

BHO Warmest Fall (Sep-Nov) 24-Hour Corrected Mean Temperature, deg F (1885-2021):

1) 55.3 in 2017
2) 55.1 in 2011
3) 54.8 in 1931
   54.8 in 2015
5) 54.4 in 2020
6) 54.3 in 1946
   54.3 in 2001
8) 54.2 in 1953
    54.2 in 2021
10) 54.1 in 2016

BHO Warmest Fall (Sep-Nov) Average Minimum Temperature, deg F (1885-2021):

1) 48.2 in 2011
2) 47.3 in 2017
3) 46.9 in 1931
4) 46.8 in 2021
5) 46.7 in 2005
   46.7 in 2015
7) 46.6 in 1946

BHO Lowest Fall (Sep-Nov) Mean Wind Speed, mph (1885-2021):

1) 11.4 in 2021
2) 11.9 in 2016
   11.9 in 2018
   11.9 in 2020
5) 12.0 in 2012
   12.0 in 2013

Mike Iacono
Chief Scientist
Blue Hill Observatory