June 2023 Summary – Cooler and Cloudier Than Average

First ripe blueberry observed on the summit of Great Blue Hill on Tuesday, June 27, 2023. Photo provided by observer Amanda Joly.

Blue Hill Observatory June 2023 Summary: 

June 2023 was cooler and cloudier than average with frequent precipitation, and it set a monthly record for low wind speed. The approximated 24-hour mean temperature for the month of 63.7 deg F was 2.0 degrees cooler than the 1891-2020 130-year average for June, and it was 0.6 degrees cooler than the 1991-2020 30-year average. The average maximum temperature of 73,3 deg F was 2.1 degrees cooler than the 30-year normal, and the average minimum temperature of 56.2 deg F was 1.4 degrees cooler than the 30-year normal. After a warm start to the month, the June turned cooler, and only nine days reached 80F or higher, including the highest temperature of 91F on the 2nd, which was the first and so far only temperature of the year of 90F or higher. The coldest temperature was 43F on the 3rd and 4th. June precipitation was frequent and totaled 4.43 inches, which was 0.20 inches less than the 30-year normal. Nearly half of the June rainfall, 1.91 inches, fell in 24 hours during periods of heavy rain on the 17th-18th. This amount included 1.29 inches in three hours during the heaviest rain showers on the afternoon of the 17th. Measurable precipitation was recorded on 17 days, which was six more than average for June, and this number tied for the fifth most on record for the month. There were eight thunderstorm days during June, which was four more than average and the most since June 2008. The first ripe blueberry of the season was observed on the summit of Great Blue Hill on the 27th, six days later than average due to the cool weather and the same date as last year. The mean wind speed was 9.2 mph, which was a new record low monthly mean wind speed for June and for any month of the year. The prevailing wind direction was from the south-southwest. The highest wind gust was only 38 mph from the south on the 14th and from the south-southwest on the 27th. June bright sunshine was below average with 195.3 hours, or 44 percent of possible, which was eleven percent less than the long-term average for the month. 

BHO Lowest June Mean Wind Speed, mph (1885-2023):

1) 9.2 in 2023
2) 9.8 in 2009
   9.8 in 2020
4) 10.3 in 1895
5) 10.4 in 2022
6) 10.5 in 2019

BHO Lowest Monthly Mean Wind Speed, mph (1885-2023):

1) 9.2 in June 2023
2) 9.5 in August 1996
   9.5 in August 2008
   9.5 in August 2021
5) 9.6 in July 2019
6) 9.7 in July 2021
7) 9.8 in July 2012
   9.8 in June 2009
   9.8 in August 2019
   9.8 in June 2020
   9.8 in July 2020

Mike Iacono
Chief Scientist
Blue Hill Observatory