July 2020 Summary – Ninth Warmest on Record

Blue Hill Observatory July 2020 Summary:

July was unusually warm and generally dry with near average sunshine. The 24-hour adjusted mean temperature for the month of 73.6 deg F was 3.9 degrees warmer than the 120-year average for July, and it was 2.8 degrees warmer than the 1981-2010 30-year average. The month tied for the ninth warmest July on record. The average maximum temperature of 83.5 deg F was nearly three degrees warmer than the 30-year mean. The average minimum temperature of 66.0 deg F was more than three degrees warmer than the 30-year mean, and it was the 2nd warmest average minimum temperature on record for July. The highest temperature observed all month was 95F on the 28th, and the lowest temperature was 57F on the 16th and 17th. There were five ninety-degree days during the month, which is two more than average for July, and this brings the total for the year up to seven. The hottest period of the month included three consecutive days of ninety or higher on the 27th to 29th, which was the first heat wave of the year. July precipitation totaled 1.72 inches, which was nearly two inches less than the long-term 120-year average and more than two inches less than the 30-year mean. The greatest precipitation in 24 hours was 0.58 inches on the 22nd-23rd, which included 0.48 inches in one hour due to a thunderstorm on the afternoon of the 23rd. There were four thunderstorm days during July, which is one less than average, and the total for the year is twelve. The mean wind speed for the month was 9.8 mph, which ties with 2012 for the second lowest on record for July, and the prevailing wind direction was from the south. The monthly peak gust was 39 mph from the south on the 11th. July sunshine was close to average with 255.0 hours of bright sunshine, or 57 percent of possible, which was one percent less than the long-term average.

BHO Warmest July Mean Temperature, deg F (1885-2020):

1) 75.1 in 2010
2) 74.9 in 1952
3) 74.5 in 2019
4) 74.1 in 1994
   74.1 in 2013
6) 74.0 in 2011
   74.0 in 2016
8) 73.8 in 1999
9) 73.6 in 2018
   73.6 in 2020

BHO Warmest July Average Minimum Temperature, deg F (1885-2020):
1) 66.9 in 2013
2) 66.0 in 2020
3) 65.9 in 2010
4) 65.6 in 1994
   65.6 in 2019
6) 65.3 in 2006
7) 65.1 in 2008

BHO Lowest July Mean Wind Speed, mph (1885-2020):

1) 9.6 in 2019
2) 9.8 in 2012
   9.8 in 2020
4) 10.0 in 2017
5) 10.1 in 1906
   10.1 in 2013

Mike Iacono
Chief Scientist
Blue Hill Observatory