July 2024 Summary – Tied for Seventh Warmest on Record – Blue Hill Observatory & Science Center

Towering cumulus with anvil passing north of Boston as viewed from Great Blue Hill on the afternoon of 1 July 2024. Photograph by Chief Observer Matt Douglas.

Blue Hill Observatory July 2024 Summary: July temperature was much above average with below average rainfall and near average sunshine. The approximated 24-hour mean temperature for the month of 74.0 deg F was 4.0 degrees warmer than the 1891-2020 130-year average for July, and it was 2.3 degrees warmer than the 1991-2020 30-year average. The month tied as the seventh warmest July on record. The average maximum temperature of 83.6 deg F was 1.9 degrees warmer than the 30-year normal. The average minimum temperature of 66.7 deg F was 2.9 degrees warmer than the 30-year normal, which was the second warmest on record. The highest temperature reached 92F on the 15th and 16th, The lowest temperature was 59F on the 26th, which tied as the warmest July monthly minimum temperature on record. July mean water vapor pressure, which is an absolute measure of water vapor in the air, was 22.2 mb, which corresponds to a mean dew point of nearly 67F. This vapor pressure was the fourth highest on record for July and the fifth highest for any month of the year. The long-term mean water vapor pressure for July is 19.0 mb, which equals a mean dew point of 62F. The total precipitation was 2.57 inches, which was 0.90 inches less than the 30-year normal. The greatest amount in 24 hours was 0.92 inches during a thunderstorm on the night of the 17th-18th, which included 0.53 inches in one hour. There were five thunderstorm days during July, which was average, and the total for the year through July was fifteen. The mean wind speed was 10.1 mph, and the prevailing wind direction was from the south-southwest. The highest wind gust was 46 mph from the south-southwest on the 31st. July sunshine was near average with 249.5 hours of bright sunshine, or 56 percent of possible, which was two percent less than the long-term average for the month. BHO Warmest July Approximated 24-Hour Mean Temperature, deg F (1885-2024): 1) 75.3 in 2022 2) 75.1 in 2010 3) 74.9 in 1952 4) 74.5 in 2019 5) 74.1 in 1994 74.1 in 2013 7) 74.0 in 2011 74.0 in 2016 74.0 in 2024 10) 73.8 in 1999 BHO Warmest July Average Minimum Temperature, deg F (1885-2024): 1) 66.9 in 2013 2) 66.7 in 2024 3) 66.0 in 2020 4) 65.9 in 2010 5) 65.7 in 2022 65.7 in 2023 7) 65.6 in 1994 65.6 in 2019 BHO Warmest July Monthly Minimum Temperature, deg F (1885-2024):(/strong> 1) 59 in 2008 59 in 2024 3) 58 in 2006 58 in 2011 58 in 2012 58 in 2019 7) 57 in 1887 57 in 2003 57 in 1994 57 in 2013 57 in 2020 57 in 2022 BHO Highest Monthly Average Vapor Pressure, mb (1932-2024): 1) 23.5 in July 2013 2) 22.9 in July 2023 3) 22.5 in July 1994 22.5 in August 2018 5) 22.2 in July 2024 6) 21.9 in August 2021 7) 21.8 in July 2020 8) 21.7 in July 2006 9) 21.6 in August 1937 10) 21.5 in August 1988 BHO Highest July Average Vapor Pressure, mb (1932-2024): 1) 23.5 in 2013 2) 22.9 in 2023 3) 22.5 in 1994 4) 22.2 in 2024 5) 21.8 in 2020 6) 21.7 in 2006 7) 21.3 in 1988 8) 21.2 in 1955 21.2 in 1975 Mike Iacono Chief Scientist Blue Hill Observatory