Late August Heat Envelops DC

Although DC’s average daily high temperatures fall to the mid-80s by late August, there have been occasional stretches of very hot weather.  Record high temperatures are still in the upper 90s and occasionally touch 100° into early September.  However, the frequency which triple-digit heat occurs in DC drops precipitously by this time of year as compared to late-June to mid-August. 

The next few days are going to be very hot and humid in the DC Metro Area.  Although no record highs are likely downtown, the combination of increasing relative humidity with high temperatures in the low-to-mid 90s will make it feel very uncomfortable.  That’s especially true after the recent fall-like weather when temperatures have been below average on five of the last eight days since DC’s last heat wave ended August 18.  A “heat wave” is defined as a minimum of three consecutive days with high temperatures of at least 90°.

DC residents will be able to compare this week’s heat wave to a similar week just two years ago.  High temperatures were in the low-to-mid 90s from August 26 – August 31, 2016.  No record high temperatures were challenged, but this six-day heat wave helped secure August 2016’s place as DC’s second hottest August on record with a monthly average temperature of 82.7° (combining daily high and low temperatures) far above the monthly average of 78.1°.

August 1998 was also a warmer than average (79.4°) month in Washington, D.C. and finished with an even more impressive streak of hot weather.  From August 22 through August 31, high temperatures in DC were in the 90s on all but one day.  A record-tying high temperature of 97° occurred on August 25, 1998.  Meanwhile, August 1993 also finished with significantly above average temperatures.  From August 25 through September 3, 1993, high temperatures were in the low-to-mid 90s.

August 2018 has been a wetter than average month with 4.85” of rain through August 26.  This month will also finish as a warmer than average month with average temperatures 1.9° warmer than average through August 26.  The last time Washingtonians had an August that finished both warmer and wetter than average was in 2011.

Record High Temperatures (Source: NOAA)

August 28

Washington, D.C., National Airport (DCA): 99° (1948)
Dulles International Airport, Sterling, VA (IAD): 98° (1993)
Baltimore, MD (BWI Airport): 101° (1948)

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August 29

DCA: 98° (1973, 1953)
IAD: 98° (1991)
BWI: 100° (1953)

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August 30

DCA: 99° (1953)
IAD: 99° (1991)
BWI: 101° (1953)