Fall 2025 Summary – Warmer and Sunnier Than Average

Blue Hill Observatory Fall (Sep-Nov) 2025 Summary: 

Fall 2025 temperature was above average, precipitation was near average, and there was more sunshine than expected. The approximated 24-hour mean temperature for fall of 53.0 deg F was 1.9 degrees warmer than the 1891-2020 130-year average for the season, and it was 0.5 degrees warmer than the 1991-2020 30-year average. The average maximum temperature of 61.7 deg F was 0.5 degrees warmer than the 30-year normal, and the average minimum temperature of 45.6 deg F was 1.1 degrees warmer than the 30-year normal. Fall 2025 began warmer than average, then it turned cooler than normal from late October through November. Fall temperature ranged from a high of 84F on September 6th to a seasonal low of 27F on November 19th,  20th, and 29th. The average water vapor pressure was 11.3 mb, which corresponded to a mean dew point of 52F. This value was higher than the long-term average vapor pressure for fall of 10.6 mb, which corresponds to an average dew point of 51F. The season was slightly drier than average, and the total precipitation was 13.13 inches, which was 0.73 inches less than the 30-year normal. Half of the fall rainfall fell during the wettest month, October, while November was much drier than average. The greatest amount in 24 hours was 2.69 inches on October 12th-13th, which was about twenty percent of the seasonal rainfall. There were four thunderstorm days during fall, which was one more than average for the season. The first and only measurable frozen precipitation of the season was observed as 0.1 inches of sleet on November 15th, and this amount was below the seasonal average snowfall of 2.5 inches. The lowest sea-level pressure during fall was 29.09 inches during the passage of an inland storm across southern New England on November 16th, and the highest sea-level pressure during fall was 30.55 inches on October 10th. The mean wind speed was 11.3 mph, which was the third lowest on record for fall, and the prevailing wind direction was from the west-northwest. The highest wind gust was 60 mph from the west as a rain storm departed the area early on October 31st. Fall sunshine was above average with 582.3 total hours of bright sunshine, or 60 percent of possible, which was six percent more than the long-term average for the season.

BHO Lowest Fall (Sep-Nov) Mean Wind Speed, mph (1885-2025):

1) 10.4 in 2023
2) 11.1 in 2024
3) 11.3 in 2025
4) 11.4 in 2021
5) 11.6 in 2016
6) 11.7 in 2022

Mike Iacono
Chief Scientist
Blue Hill Observatory