June 2020 Summary – Tenth Wettest on Record

Blue Hill Observatory June 2020 Summary:

June was unusually warm and wet with more sunshine than average. The 24-hour adjusted mean temperature for the month of 67.5 deg F was 3.4 degrees warmer than the 120-year average for June, but it was just 2.2 degrees warmer than the 1981-2010 30-year average. The month was the 11th warmest June on record. The average maximum temperature of 78.0 deg F was nearly three degrees warmer than the 30-year mean. The average minimum temperature of 59.1 deg F was more than two degrees warmer than the 30-year mean, and it was the 5th highest average minimum temperature on record for June. The highest temperature observed all month was 90F on the 20th and 21st, and the lowest temperature was 42F on the 1st. June precipitation totaled 7.56 inches, which was nearly four inches more than the long-term 120-year average and three and a quarter inches more than the 30-year mean. The month was the tenth wettest June on record. Torrential rain during several thunderstorms on the 28th amounted to 3.27 inches, which surpassed the previous record for the date of 2.09 inches in 1938. This was the seventh wettest calendar day on record during June at the Observatory. The greatest precipitation in 24 hours was 4.71 inches on the 28th-29th, which included 1.53 inches in a single hour and 2.45 inches over two hours during thunderstorms on the afternoon of the 28th. There were five thunderstorm days during June, which is one more than average, and the total for the year is up to eight, which is one less than average. The mean wind speed for the month was 9.8 mph, which ties with 2009 for the lowest on record for June, and the prevailing wind direction was from the south. The monthly peak gust was 55 mph from the southwest during a thunderstorm on the 6th. Despite being wet, June was sunnier than average with 266.6 hours of bright sunshine, or 61 percent of possible, which was six percent more than the long-term average.

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

1) 59.9 in 1925
2) 59.8 in 2001
3) 59.7 in 1999
4) 59.5 in 2008
5) 59.1 in 2020
6) 59.0 in 1922
   59.0 in 1976
8) 58.9 in 1973
   58.9 in 2010
10) 58.8 in 1994

BHO Highest June Precipitation, inches (1885-2020):

1) 17.32 in 1998
2) 13.73 in 1982
3) 12.31 in 2006
4) 12.11 in 2013
5) 10.78 in 1922
6) 9.03 in 1938
7) 8.77 in 1931
8) 8.64 in 1920
9) 8.02 in 1959
10) 7.56 in 2020

BHO Wettest June Calendar Days, inches (1885-2020):

1) 6.07 on 13 June 1998
2) 4.01 on 7 June 2006
3) 3.92 on 19 June 1922
4) 3.61 on 6 June 2000
5) 3.36 on 18 June 1998
6) 3.28 on 7 June 2013
7) 3.27 on 28 June 2020
8) 3.15 on 6 June 1986
9) 3.04 on 30 June 1921

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

1) 9.8 in 2009
   9.8 in 2020
3) 10.3 in 1895
4) 10.5 in 2019
5) 10.6 in 2005
   10.6 in 2008
   10.6 in 2011
   10.6 in 2014

Mike Iacono
Chief Scientist
Blue Hill Observatory