August 2020 Summary – Sixth Warmest on Record

| September 8, 2020 | Reply
Lightning over Boston as viewed from Blue Hill Observatory during a thunderstorm on 28 June, 2020. Photograph by Samantha Richard.

Blue Hill Observatory August 2020 Summary:

August was unusually warm and generally dry with above average sunshine. The 24-hour adjusted mean temperature for the month of 72.3 deg F was 4.2 degrees warmer than the 120-year average for August, and it was 2.9 degrees warmer than the 1981-2010 30-year average. The month tied with 2005 as the sixth warmest August on record. The average maximum temperature of 82.5 deg F was more than three degrees warmer than the 30-year mean, and it tied for the fifth warmest average maximum on record. The average minimum temperature of 64.3 deg F was about three degrees warmer than the 30-year mean, and it tied for the seventh warmest average minimum temperature on record for August The highest temperature observed all month was 94F on the 10th, which was part of a four-day heat wave (the second of the summer) from the 9th to the 12th. The lowest temperature was 54F on the 31st. There were six ninety-degree days during the month, which is four more than average for August and the most in August since 2002, and this number brings the total for the year up to 13. The year to date for January through August was the fourth warmest on record. August precipitation totaled 3.74 inches, which was about three-tenths of an inch less than the long-term 120-year average and the 30-year mean. The greatest precipitation in 24 hours was 2.21 inches on the 23rd, which included 1.36 inches in a single hour. Hail of up to a half-inch in diameter was observed along with the heavy rain during strong thunderstorms on the 23rd. There were five thunderstorm days during August, which is one more than average for the month, and the total for the year is 17. The mean wind speed for the month was 10.6 mph, and the prevailing wind direction was from the south-southwest. The monthly peak gust was 67 mph from the south-southeast on the 4th, which was caused by the passage of Tropical Storm Isaias passing northward through western New England while also bringing 0.21 inches of rain to the Observatory. August sunshine was above average with 255.3 hours of bright sunshine, or 62 percent of possible, which was four percent more than the long-term average.

BHO Warmest August 24-Hour Adjusted Mean Temperature, deg F (1885-2020):

1) 74.1 in 2016
2) 73.4 in 2018
3) 72.6 in 2012
4) 72.5 in 1988
5) 72.4 in 2015
6) 72.3 in 2005
72.3 in 2020
8) 72.1 in 2002
9) 72.0 in 2001

BHO Warmest August Average Maximum Temperature, deg F (1885-2020):

1) 85.1 in 2016
2) 83.2 in 2005
3) 83.1 in 1949
4) 82.6 in 2015
5) 82.5 in 1988
82.5 in 2002
82.5 in 2012
82.5 in 2020

BHO Warmest August Average Minimum Temperature, deg F (1885-2020):

1) 66.4 in 2018
2) 65.0 in 2016
3) 64.9 in 2001
4) 64.6 in 2012
5) 64.4 in 2015
64.4 in 2015
7) 64.3 in 2003
64.3 in 2020

Summer (June-August) 2020 Summary:

Summer 2020 was exceptionally warm and sunnier than average with periods of rain that prevented more severe drought conditions from developing. The 24-hour adjusted mean temperature for Summer of 71.1 deg F was 3.8 degrees warmer than the 120-year average for June-August, and it was 2.6 degrees warmer than the 1981-2010 30-year average. The season was the third warmest Summer on record. There were two heat waves, one from July 27th to 29th and the other from August 9th to 12th with the highest temperature reaching 95 deg F on July 28th. Precipitation totaled 13.02 inches, mostly due to the 7.56 inches observed during the tenth wettest June on record. The Summer total was about one and a half inches more than the long-term mean and about three-quarters of an inch more than the 30-year mean. The greatest rainfall in 24 hours was 4.71 inches on June 28th-29th during strong thunderstorms. A little over eight inches of the seasonal rain fell on only four calendar days with excessive rain of an inch or more. Among the rainfall events during the season was the impact of Tropical Storm Isaias, which brought 0.21 inches of rain and a peak gust to 67 mph from the SSE on August 4th. Hail of up to one-inch in diameter was observed during strong thunderstorms on August 23rd. There were fourteen thunderstorm days during Summer, one more than average. The season brought 60 percent of the possible bright sunshine, which was three percent more than the long-term average.

BHO Warmest Summer (Jun-Aug) 24-Hour Adjusted Mean Temperature, deg F (1885-2020):

1) 71.6 in 2016
2) 71.3 in 2010
3) 71.1 in 2020
4) 70.9 in 2018
5) 70.8 in 1949

Mike Iacono
Chief Scientist
Blue Hill Observatory

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