DC’s cool and dry August

 

NOAA's temperature outlook for late-August

Washingtonians have enjoyed fall-like temperatures for much of August. That’s despite August traditionally being the second hottest month of the year in the nation’s capital. It has also been an unusually dry month across the D.C. metropolitan area. This combination goes against the recent trend for warmer and wetter than average August’s.

August got off to a cooler than average and fall-like start in the nation’s capital. The first 90-degree August day didn’t occur until August 12. This month’s longest heat wave was a modest four-day stretch from August 13 – 16. A “heat wave” is loosely defined as a minimum of three consecutive 90-degree days. 

The nation’s capital has an August total of only five 90-degree days so far and no more are expected during the final week of the month. That would be DC’s lowest such total of 90-degree August days since 2014. The average monthly temperature so far this August is nearly three degrees below average. The nation’s capital hasn’t had such a cool August since 2004, which finished 3.5 degrees below average. 

This has also been a very dry month in the nation’s capital with only 0.11 inches of rain as of August 19, making it among the driest on record. Of course, it would only take a downpour at National Airport to boost this month’s rainfall total. However, the August trend in Washington, D.C. has been for largely dry conditions with only isolated showers and storms.

Other dry August’s in the nation’s capital have given way to dry September’s such as in 2019. That’s when August had only 1.99” of rain (1.26” below average) and was followed by DC’s fourth driest September (0.25”). September is also the most active month in the tropical Atlantic and the remnants of a decaying tropical system could help bring the DMV (DC, Maryland and Virginia) widespread, beneficial rainfall. The precipitation outlook for the DMV from NOAA’s Climate Prediction Center through September 2 is for near average rainfall.

Driest August’s in Washington, D.C. (Source: NOAA)

1. 0.55” (1962)
2. 0.59” (1998)
3. 0.62” (1930)
4. 0.74” (1943)
5. 0.77” (1917)
6. 0.85” (1892)
7. 0.88” (1995)
8. 1.01” (1884)
9. 1.03” (2006)
10. 1.07” (1881)

Average – 3.25”