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... Extremely High Dewpoints During Meteorological Summer...


The meteorological summer /June through August/ will most certainly be remembered not so much for record breaking heat /there were very few record high temperatures set across the area/...but a stifling combination of heat and humidity that kept coming in waves. The humidity...in particular...made for many uncomfortable afternoons across the area...and also led to muggy nights where the temperatures remained in the 70s. Dewpoints during the meteorological summer flirted with record values...and had it not been for the most recent late august intrusion of drier air...the summer may have broken records for the highest average dewpoint in recorded history.

Dewpoint is a measure of moisture in the air that is often compared to relative humidity. Relative humidity is the amount of moisture relative /hence the name/ to the air temperature. High relative humidities happen year-round...but we seldom feel uncomfortable in high humidity except for the summertime. A 60 percent humidity on a 40 degree day means little to us. However...a 60 percent humidity on a 90 degree day means heat advisories are issued and conditions can become dangerous. so instead of humidity...the dewpoint becomes the focus for summertime discomfort as a better and more accurate representation of moisture in the air.

At the three large metro areas in the NWS Wilmington forecast area...near record dewpoints were seen this summer.

CINCINNATI AREA
---------------

Hourly dewpoint observations in the Cincinnati metro area were analyzed back to 1930...a period of 80 years. For the period from 1930 to 1947...observations from Lunken field /LUK/ were used...and from 1948 through August 31 2010...observations from the greater Cincinnati airport /CVG/ were used. Below is a table of the highest average hourly dewpoint for the summer season...and the highest individual hourly dewpoint measured during that respective summer for the Cincinnati metro area since 1930.


YEAR       AVERAGE DEWPOINT        MAX HOURLY DEWPOINT MEASURED
----------------------------------------------------------------
1995             66.6                         79
1943             66.3                         82
2010**           65.9                         77
1977             65.7                         78
1998             65.5                         78
1980             65.3                         78
1942             65.3                         77
1935             65.0                         79
1949             65.0                         77
1937             65.0                         79

The highest observed dewpoint ever measured in the available records is 82 degrees at 5 pm on July 17th 1943. Dewpoints of 80 degrees or more have only been measured 11 times in the past 80 years in Cincinnati...most recently on June 19th 1975 at 6 pm.

Not only were the dewpoints high this summer...but warm temperatures made for one of the warmer summers in Cincinnati history. According to records dating back to 1872 in the Cincinnati area...the summer of 2010 will go down as the 12th warmest summer ever recorded. Below is a table of the 15 warmest meteorological summers in the Cincinnati area. it could be argued that summer 2010 was the most uncomfortable ever in terms of combined heat/humidity...with only the summer of 1943 showing similar combinations of high heat and humidity.


YEAR            AVERAGE SUMMER TEMPERATURE
------------------------------------------
1934                    78.8
1936                    78.7
1874                    78.6
1881                    78.4
1901                    78.0
1913                    77.6
1872                    77.6
1876                    77.5
1914                    77.4
1873                    77.3
1944                    77.2
2010                    77.0**
1898                    77.0
2007                    76.8
1943                    76.8

COLUMBUS AREA
--------------

Hourly dewpoint observations in the Columbus metro area were analyzed back to 1930...a period of 80 years. Below is a table of the highest average hourly dewpoint for the summer season...and the highest individual hourly dewpoint measured during that respective summer for the Columbus metro area since 1930.



YEAR       AVERAGE DEWPOINT        MAX HOURLY DEWPOINT MEASURED
----------------------------------------------------------------
1995             66.0                         80
1975             65.7                         77
1949             64.7                         77
1987             64.4                         77
2010             63.8                         78
1943             63.8                         77
1947             63.7                         77
2002             63.3                         75
1980             63.3                         80
1993             63.3                         79

The highest observed dewpoint ever measured in the available records is 80 degrees which occurred three different times...most recently at 9 pm on July 27th 1997. Dewpoints of 80 degrees or more have only been measured 4 times in the past 80 years in Columbus. Not only were the dewpoints high this summer...but warm temperatures made for one of the warmer summers in Columbus. According to records dating back to 1879 in the Columbus area...the summer of 2010 will go down as tied for the 5th warmest summer ever recorded. Below is a table of the 10 warmest meteorological summers in the Columbus area. It could be argued that summer 2010 was the most uncomfortable in the last 80 years in terms of combined heat/humidity...with only the summers of 1995...2002 and 1949 showing similar combinations of high heat and humidity.



YEAR            AVERAGE SUMMER TEMPERATURE
------------------------------------------
1934                    77.1
1936                    76.6
1901                    76.0
2005                    76.0
1999                    75.9
2002                    75.9
2010                    75.9
1995                    75.8
1991                    75.8
1949                    75.6

DAYTON AREA
-------------

Hourly dewpoint observations in the Dayton metro area were analyzed back to 1937...a period of 73 years. Below is a table of the highest average hourly dewpoint for the summer season...and the highest individual hourly dewpoint measured during that respective summer for the Dayton metro area since 1937.


YEAR       AVERAGE DEWPOINT        MAX HOURLY DEWPOINT MEASURED
----------------------------------------------------------------
1995             65.5                         78
1973             63.6                         75
1949             63.6                         77
1981             63.5                         78
2010             63.4                         78
1993             63.4                         76
1980             63.1                         80
1989             62.9                         76
1987             62.9                         77
1975             62.7                         75

The highest observed dewpoint ever measured in the available records is 80 degrees which occurred 18 different times...most recently at 1 pm on July 30th 1999. Not only were the dewpoints high this summer...but warm temperatures made for one of the warmer summers in Dayton. According to records dating back to 1878 in the Dayton area...the summer of 2010 will go down as tied for the 12th warmest summer ever recorded. Below is a table of the 15 warmest meteorological summers in the Dayton area. It could be argued that summer 2010 was the most uncomfortable in the last 73 years in terms of combined heat/humidity...with only the summer of 1995 showing similar combinations of high heat and humidity.



YEAR            AVERAGE SUMMER TEMPERATURE
------------------------------------------
1934                    77.9
1936                    77.7
1901                    76.8
1921                    76.0
1900                    76.0
1988                    75.6
1995                    75.6
1954                    75.5
1944                    75.5
1931                    75.5
1933                    75.4
1952                    75.2
2002                    75.2
2010                    75.2


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Page last modified: January 28, 2011.
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