The Hottest Time of the Year

The second half of July and first half of August is traditionally the hottest time of the year for much of the United States.  Washington, D.C. hottest temperature on record (106°) has occurred twice: once on July 20, 1930 and August 6, 1918.  The National Weather Service is responsible for keeping weather records for the United States.

The Nation’s Capital averages 36 days of 90°/+ temperatures in a given year, with the majority coming during meteorological summer from June 1 through August 31.  So far this year, Washingtonians have sweat through 27 days of 90° heat.  The record for highest number of 90° days in a given year is 67 that occurred twice (1980, 2010), while the lowest such total was seven most recently in 1905.  Although there were 58 days that reached or exceeded 90° in Washington, D.C. last year, only five such days occurred through July 4.

Residents of the DC Metro Area are well-positioned to experience another summer with a higher than average number of 90° days.  A “heat wave” is defined as any stretch of three or more consecutive days with temperatures of at least 90°.  The longest heat wave so far this summer has been six days.  However, the current heat wave, that began July 17, is poised to continue through at least next Monday, which would make it the longest heat wave of 2017.  The longest heat wave of 2016 was 13 days from July 21 through August 2.  

Last summer was the third hottest on record in the Nation’s Capital.  This summer has seen a significantly higher number of 90° days to this point (26) than last year (16).  However, there were also four days of triple-digit heat in the Nation’s Capital last year and there haven’t been any so far this year.

While no 100° heat has occurred yet this summer, there will be several chances to reach the century mark during the next several days.  Whether or not this happens, this summer has already had the tenth hottest June on record (average monthly temperature of 77.3°) and the sixth warmest July (82.8°) through July 19.    

Record Highs (Degrees Fahrenheit)  Source: NWS

July 20

DCA: 106° (1930) --> Tied with August 6, 1918 for hottest DC temperature on record
IAD: 101° (1980)
BWI: 102° (1930)

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July 21

DCA: 104° (1926)
IAD: 101° (1991)
BWI: 104° (1930)

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July 22

DCA: 103° (1926)
IAD: 105° (2011)  --> Hottest temperature on record at Dulles Airport
BWI: 106° (2011)

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July 23

DCA: 102° (2011)
IAD: 99° (2011)*
BWI: 102° (2011)*

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July 24

DCA: 101° (2010)
IAD: 99° (2010)
BWI: 101° (2010)

*= also occurred in previous years