July 2018 Summary – Eighth Warmest and Eighth Sunniest on Record

Blue Hill Observatory

July 2018 Summary:

July was much warmer and sunnier than average with near normal precipitation. The 24-hour adjusted mean temperature for the month of 73.6 deg F was 3.9 degrees warmer than the 120-year average for July and about three degrees warmer than the 1981-2010 30-year average. This mean temperature was the eighth warmest on record for July and the warmest only since 2016. The average maximum temperatures for July of 83.9 deg F tied for the ninth warmest on record. There were five ninety-degree days, which is two more than average, and the yearly total is up to seven, which is three more than average through July. The highest temperature for the month was 94F on the 1st and 3rd, and the lowest temperature was 54F on the 7th. A total of 3.84 inches of precipitation was measured, which was slightly more than the long-term 120-year average and slightly less than the 30-year mean. About one-third of the monthly total, 1.36 inches, was the greatest amount to fall in 24 hours on the 17th-18th, and about one inch of this amount occurred in a single hour during a strong thunderstorm on the afternoon of the 17th. There were five thunderstorm days during July, average for the month, which brought the annual total up to 11. The mean wind speed was 10.4 mph, and the prevailing direction was from the south. A peak gust of 41 mph from the south-southwest occurred on the 26th. July was much sunnier than average with a total of 310.7 hours of bright sunshine, or 70 percent of possible, which was 12 percent more than the long-term mean, making July the eighth sunniest on record.

BHO Warmest July Mean Temperature (24-hr adjusted mean), deg F (1885-2018):

1)  75.1 in 2010
2)  74.9 in 1952
3)  74.1 in 1994
   74.1 in 2013
5)  74.0 in 2011
   74.0 in 2016
7)  73.8 in 1999
8)  73.6 in 2018
9)  73.5 in 1949
10) 73.2 in 2012

BHO Warmest July Average Maximum Temperature, deg F (1885-2018):

1)  87.2 in 1952
2)  86.5 in 2010
3)  85.5 in 1949
4) 84.9 in 1994
5)  84.7 in 2016
6) 84.5 in 1911
7)  84.4 in 1983
8)  84.3 in 1999
9)  83.9 in 1955
   83.9 in 1995
   83.9 in 2018

BHO Greatest July Sunshine, hours [percent] (1885-2018):

1)  331.6 in 1952   [75%] 2)  326.4 in 1966   [73%] 3) 317.3 in 1899   [71%] 4)  317.0 in 1909   [71%] 5)  316.4 in 2001   [71%] 6) 314.0 in 1893   [71%] 7)  313.6 in 1968   [71%] 8) 310.7 in 2018   [70%] 9) 309.3 in 1900   [70%] 10) 306.8 in 1892   [69%]

BHO Greatest July Water Vapor Pressure, mb (1932-2018):

1) 23.5 in 2013
2) 22.5 in 1994
3) 21.7 in 2006
4) 21.3 in 1988
5) 21.2 in 1955
   21.2 in 1975
7) 21.0 in 1967
8) 20.8 in 2018
9) 20.7 in 2008

Mike Iacono
Chief Scientist
Blue Hill Observatory