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”

How does Erin compare to other Category 5 hurricanes?

 

Erin at peak intensity, August 2025 (Source: NOAA)

Hurricane Erin rapidly intensified into a Category 5 storm on August 16 with maximum sustained winds of 160 mph and a minimum central air pressure of 915 millibars (mb). By comparison, standard sea level air pressure is approximately 1013 mb. Fortunately, Erin has weakened and isn’t expected to have any direct impacts in the United States.

Category 5 hurricanes are rare since they require these ideal circumstances to develop: warm ocean water to a sufficient depth without any wind shear. When they do form, they typically don’t remain at Category 5 intensity for long since very strong hurricanes go through something known as the “eyewall replacement cycle.” That’s when the inner eyewall, where the strongest winds are, collapses and is replaced by a larger, outer eyewall with weaker winds.

Category 5 hurricanes also tend to be cyclical with few or none for sustained periods of time. For example, a combined total of only five Category 5 Atlantic hurricanes developed in the 1980s and 1990s (Allen, Gilbert, Hugo, Andrew and Mitch). That was followed by eight over a five-year period from 2003 – 2007, including four in 2005 (Emily, Katrina, Rita and Wilma). None occurred for nine years after that until 2016.

When Hurricane Erin reached Category 5 intensity on August 16, it became the eleventh Category 5 Atlantic hurricane over the last nine years. Fortunately, not all of them have made landfall. But, Hurricane Michael in 2018 became only the fourth Category 5 hurricane on record to make landfall in the United States. 

Hurricane Erin’s lowest minimum central air pressure of 915 mb tied it with two other historic Category 5 Atlantic storms. Hurricane Isabel in 2003 and the infamous November 1932 hurricane each had a minimum air pressure of 915 mb at their peak intensities. Hurricanes and tropical storms didn’t start receiving names until the 1950s, so before that they were often referred to by using geographic references.

The November 1932 hurricane holds the Atlantic record for longest hurricane to maintain Category 5 intensity at three days and six hours. More recently, 2017’s Hurricane Irma was at Category 5 intensity for three days. By comparison, Hurricane Erin was a Category 5 storm for 8 hours and 40 minutes. Hurricanes can sometimes weaken below Category 5 intensity and then regain Category 5 status.

Weather Quiz

 

August in the nation's capital

True or False.

August is the second hottest month of the year in the nation’s capital.