Hottest Weather of the Summer ?

DC’s hottest weather of the summer will arrive later this week.  That’s typically the hottest time of the year in the Nation’s Capital.  Average high temperatures are at their pinnacle (89°) from July 7 through July 22.  In that time, all but two record high temperatures are at least 100°.  A “heat wave” is defined as any period of three or more consecutive days with high temperatures of at least 90°.
 

The current heat wave began on July 11 and will continue through at least next Monday, July 22.  A heat wave of at least 12 days would tie for DC’s fifth longest one of the last 20 years.  The Nation’s Capital has had two 12-day heat waves in the last two decades.  One was from August 10 – August 21, 2016 and the other was from July 14 – July 25, 2010.  The longest heat wave Washingtonians have experienced in the last 20 years was 18 days from July 22 – August 8, 1999.

There have been some other noteworthy heat waves in the Nation’s Capital.  Perhaps the most noteworthy was an 11-day heat wave from June 28 – July 8, 2012.  While not as long as some others, high temperatures reached or exceeded 100° five times in that 11-day span.  That included June’s hottest temperature on record (104° on June 29) in Washington, D.C., and its second hottest overall temperature (105°) on July 7.

Triple-digit heat is a rarity in Washington, D.C., typically occurring only every few years.  The last time DC residents experienced 100° was August 15, 2016.  However, the Nation’s Capital is poised to approach the century mark on Friday, Saturday and Sunday.  Even if high temperatures remain in the 90s, the increasing relative humidity will make it feel much hotter.  The “heat index” which is what people feel when you combine the air temperature with the relative humidity, will feel like 105° – 110°.  Those are dangerously hot conditions and any outdoor activities should be done early in the day when temperatures are cooler.  Air quality is also the best early in the day.

Since July 16 is my birthday, I want to mention that DC’s record high temperature today is 104° set in 1988.  High temperatures today are in the 90s which, while above average, aren’t close to record levels.  The high temperature on July 16 last year was 98°.  That turned out to be DC’s hottest temperature in all of 2018.  DC’s coolest July 16 high temperature was 75° in 1962.

Record High Temperatures (Source: National Weather Service)

July 19:

Washington, D.C., National Airport (DCA): 102° (1930)
Dulles Airport (IAD), Sterling Virginia: 98° (1977)
Baltimore, MD (BWI Airport): 103° (1930)

July 20:

DCA: 106° (1930) – DC’s hottest July temperature on record
IAD: 101° (1980)
BWI: 102° (1930)


July 21:

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