June 2025 Summary – Eighth Warmest on Record
Blue Hill Observatory June 2025 Summary:
June temperature was well above average with much below normal rainfall and average sunshine. The approximated 24-hour mean temperature for the month of 68.1 deg F was 3.8 degrees warmer than the 1891-2020 130-year average for June, and it was 2.4 degrees warmer than the 1991-2020 30-year average. The month was the eighth warmest June on record. The average maximum temperature of 78.5 deg F was 3.1 degrees warmer than the 30-year normal. The average minimum temperature of 59.8 deg F was 2.2 degrees warmer than the 30-year normal, which tied as the third warmest on record. Eighteen days during the month were warmer than normal, including seven days that reached or exceeded ninety degrees, which was the largest number of ninety-degree days ever observed in June at Blue Hill. A four-day heat wave occurred on June 22nd-25th, which was one of only three four-day heat waves ever recorded in June. The highest temperature for the month was 99F on June 24th, which matched the highest temperature ever measured at Blue Hill during June and surpassed the previous record for the date of 91F set in 1914, 1976, and 2013. The minimum temperature on June 24th was 76F, which was the second highest daily minimum temperature in June on record and surpassed the previous record for the date of 70F set in 1909. This reading was matched the following day on June 25th, when the low of 76F surpassed the previous record for that date of 71F set in 1909. The lowest temperature during June was 47F on the 1st. June mean water vapor pressure, which is an absolute measure of water vapor in the air, was 17.9 mb, which corresponded to a mean dew point of about 60F. This amount was well above the long-term mean water vapor pressure for June of 15.4 mb, which equals a mean dew point of about 56F. The total precipitation was 1.49 inches, which was 3.14 inches less than the 30-year normal. The greatest amount in 24 hours was 0.95 inches on the 7th, and only 0.54 inches of rain fell during the last three weeks of the month. Despite the frequent heat, there was only one thunderstorm day during the month on the 7th, which was one fewer than average, and the total for the year through June increased to eight. The first ripe blueberry of the season was observed on the summit of Great Blue Hill on June 23rd, which was two days later than average. The mean wind speed was 10.1 mph, which was the fourth lowest on record for June, and the prevailing wind direction was from the east-northeast. The highest wind gust was 52 mph from the west-northwest during the arrival of some briefly cooler air on the 20th. June sunshine was near average with 243.0 hours of bright sunshine, or 55 percent of possible, which matched the long-term average for the month.
BHO Warmest June Approximated 24-Hour Mean Temperature, deg F (1885-2025):
1) 70.0 in 2021
2) 68.7 in 1999
3) 68.5 in 2001
4) 68.4 in 2024
5) 68.3 in 1925
68.3 in 1930
7) 68.2 in 1994
8) 68.1 in 2025
9) 68.0 in 1943
10) 67.9 in 1976
BHO Warmest June Average Minimum Temperature, deg F (1885-2025):
1) 60.4 in 2021
2) 59.9 in 1925
3) 59.8 in 2001
59.8 in 2025
5) 59.7 in 1999
6) 59.5 in 2008
7) 59.1 in 2020
8) 59.0 in 1922
59.0 in 1976
BHO Longest June Heatwaves, days (1885-2025):
1) 4, 3-6 June 1925 (93/94/91/95)
4, 7-10 June 2008 (91/91/94/98)
4, 22-25 June 2025 (91/94/99/93)
4) 3, 3-5 June 1919 (98/99/92)
3, 19-21 June 1923 (92/91/90)
3, 13-15 June 1956 (92/93/92)
3, 8-10 June 1984 (94/92/92)
3, 13-15 June 1988 (93/92/94)
3, 27-29 June 1991 (91/95/91)
3, 17-19 June 1994 (91/93/90)
3, 26-28 June 1999 (90/93/91)
3, 20-22 June 2012 (93/94/93)
3, 6-8 June 2021 (91/92/92)
3, 28-30 June 2021 (93/95/94)
3, 18-20 June 2024 (92/93/94)
BHO Highest June Number of Ninety-Degree Days (1885-2025):
1) 7 in 2025
2) 6 in 1997
6 in 2021
4) 5 in 1923
5 in 1984
5 in 1988
5 in 1999
8) 4 in 1925
4 in 1949
4 in 1991
4 in 2008
BHO Highest June Daily Maximum Temperature, deg F (1885-2025):
1) 99 on June 4, 1919
99 on June 24, 2025
3) 98 on June 3, 1919
98 on June 10, 2008
5) 96 on June 26, 1952
6) 95 on June 6, 1925
95 on June 5, 1930
95 on June 28, 1991
95 on June 29, 2021
BHO Highest June Daily Minimum Temperature, deg F (1885-2025):
1) 78 on June 6, 1925
2) 76 on June 24, 2025
76 on June 25, 2025
4) 75 on June 4, 1919
5) 74 on June 2, 1918
74 on June 5, 1925
74 on June 21, 1923
74 on June 21, 2012
BHO Highest June Mean Water Vapor Pressure, mb (1932-2025):
1) 18.1 in 2021
2) 18.0 in 1973
3) 17.9 in 2005
17.9 in 2025
5) 17.7 in 1976
6) 17.6 in 1889
17.6 in 2006
8) 17.5 in 2010
BHO Lowest June Mean Wind Speed, mph (1885-2025):
1) 9.2 in 2023
2) 9.8 in 2009
9.8 in 2020
4) 10.1 in 2025
5) 10.3 in 1895
Mike Iacono
Chief Scientist
Blue Hill Observatory
