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Blue Hill Observatory June 2026 Summary:
June 2026 was exceptionally warm with below average precipitation and much above average sunshine. The approximated 24-hour mean temperature for the month of 69.7 deg F was 5.4 degrees warmer than the 1891-2020 130-year average for June, and it was 4.0 degrees warmer than the 1991-2020 30-year average. The average maximum temperature of 80.8 deg F was 5.4 degrees warmer than the 30-year normal, and it was the second warmest on record. The average minimum temperature of 59.5 deg F was 1.9 degrees warmer than the 30-year normal, which tied as the sixth warmest on record. The warmth persisted all month; only four days were cooler than average, and seventeen days reach 80F or warmer. The highest temperature was 91F on the 12th, one of two ninety-degree days, and the lowest temperature was 45F on the 1st and 2nd. June mean water vapor pressure, which is an absolute measure of water vapor in the air, was 16.8 mb, which corresponded to a mean dew point of about 59F. This amount was above the long-term mean water vapor pressure for June of 15.4 mb, which equals a mean dew point of about 56F. June was much drier than average with a total precipitation of 1.86 inches, which was 2.77 inches less than the 30-year normal, and only nine days had measurable precipitation. The greatest amount in 24 hours was 0.64 inches, which fell in less than two hours during heavy rain showers on the 18th. Dry weather has persisted since last fall, and the total precipitation for the eight months from November 2025 to June 2026 was just 23.54 inches, which was the sixth driest on record for that period. As a result, much of eastern Massachusetts was under severe drought at the end of June. There were three thunderstorm days during the month, which was one fewer than average, and the annual total through June is six. The first ripe blueberry was observed on the summit of Great Blue Hill on June 24th, which was three days later than the long-term average date. The highest sea-level pressure was 30.29 inches on the 8th, and the lowest sea-level pressure was 29.47 inches during a rain storm with strong southerly winds on the 18th. The mean wind speed was very low at 10.2 mph, and the prevailing wind direction was from the west-northwest. The highest wind gust was 51 mph from the south on the 18th. June sunshine was much above average with 302.2 hours of bright sunshine, or 69 percent of possible, which was 14 percent more than the long-term average for the month. June 2026 was the seventh sunniest on record and the sunniest since the monthly record of 336.1 hours, or 76 percent of possible, was set in June 1971.
BHO Warmest June Approximated 24-Hour Mean Temperature, deg F (1885-2026):
1) 70.0 in 2021
2) 69.7 in 2026
3) 68.7 in 1999
4) 68.5 in 2001
5) 68.4 in 2024
6) 68.3 in 1925
68.3 in 1930
8) 68.2 in 1994
9) 68.1 in 2025
10) 68.0 in 1943
BHO Warmest June Average Maximum Temperature, deg F (1885-2026):
1) 80.9 in 2021
2) 80.8 in 2026
3) 80.4 in 1930
4) 80.3 in 1949
5) 79.6 in 2024
6) 79.5 in 1957
79.5 in 1976
8) 79.3 in 1943
79.3 in 1999
BHO Warmest June Average Minimum Temperature, deg F (1885-2026):
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
59.5 in 2026
8) 59.1 in 2020
9) 59.0 in 1922
59.0 in 1976
BHO Lowest November-June Precipitation, inches (1886-2026):
1) 20.84 in 1980-1981
2) 21.81 in 1893-1894
3) 22.23 in 1984-1985
4) 22.86 in 1965-1966
5) 23.11 in 1943-1944
6) 23.54 in 2025 2026
7) 23.68 in 1931-1932
8) 23.93 in 1964-1965
9) 24.00 in 1917-1918
10) 24.35 in 1904-1905
BHO Highest June Bright Sunshine, hours (1886-2026):
1) 336.1 in 1971 [76%]
2) 335.5 in 1908 [76%]
3) 327.4 in 1953 [74%]
4) 322.6 in 1949 [73%]
5) 313.7 in 1912 [71%]
6) 309.1 in 1965 [70%]
7) 302.2 in 2026 [69%]
8) 301.6 in 2016 [69%]
Mike Iacono
Chief Scientist
Blue Hill Observatory
