DC’s rainy end to September

 

A September day in NW Washington, D.C.

This month’s weather in the nation’s capital stands out more than many recent Septembers. It has featured no shortage of cooler than average weather and is coming to a damp and wet conclusion. Despite the cloudy and wet weather over the past week, this month will still finish as drier than average month.

September is DC’s fourth rainiest month of the year with a monthly average of 3.93”, according to NOAA. Despite the gloomy weather of the last week, this month will finish with less than 3” of rain. That will make this the third consecutive drier than average September in Washington, D.C.

Oddly enough, this month will also finish with near average temperatures despite being the fourth warmest month of the year on average. Nine of the first 10 days of September were cooler than average and DC’s temperature average has remained below average for much of the month since then. This September will finish as DC’s first without any 90-degree heat since 2011. That’s in contrast to recent Septembers such as 2019 that featured nine days of 90-degree heat and last September that featured five consecutive days in the upper 90s.

In recent decades, cooler than average September’s have largely been a function of above average rainfall in the nation’s capital such as in 1999, 2011 and 2020. However, this month will finish with below average rainfall despite the gloomy weather over the last week. The DMV could actually use some beneficial rainfall, especially areas west of I-95 where drought conditions remain in effect. 

The cooler than average temperatures this month have been a relief to many following DC’s third hottest summer. The 2024 summer was not only very hot, it was also quite dry and that acerbated the drought conditions, particularly in areas along and west of I-81. That will be significant as the leaves start to change color. Traditionally, the autumn colors are more muted following a hot and dry summer.

Recent hurricanes punish Florida

 

Hurricane Ian, September 2022 (Source: WUSA9)

Hurricane Helene will be the fifth hurricane to make landfall in the state of Florida since 2022. It’s vital to listen to your state and local authorities during any landfalling tropical system to ensure your safety. Here’s a closer look at other recent hurricanes to impact Florida.

Debby (2024): A minimal, Category 1 hurricane with sustained winds of 80 mph, Debby made landfall in the Florida panhandle on August 5. It moved offshore on August 6 as a weak tropical storm after a slow track across the southeastern United States. It made a second landfall on August 7 as a 60 mph tropical storm in South Carolina. The DC Area saw heavy rain and gusty winds from its remnants, including an August 8 rainfall record of 1.39” at Dulles Airport. Ten deaths in the United States were attributed to Debby.

Idalia (2023): This was a power Category 4 storm at peak intensity with sustained winds of 130 mph and a minimum central air pressure of 940 millibars (mb). Fortunately, Idalia weakened to Category 3 intensity before its landfall in the “Big Bend” area of the Florida panhandle. Idalia was the strongest hurricane to make landfall in this part of Florida since 1950. A significant storm surge occurred, along with widespread tree damage in inland areas. Despite causing an estimated $3.6 billion in damages, according to NOAA, the name “Idalia” wasn’t retired. Twelve fatalities were attributed to Idalia.

Nicole (2022): While Nicole wasn’t a major hurricane, it had major impacts in the United States.  Nicole came ashore near Vero Beach on November 10 as a Category 1 storm with sustained winds of 75 mph. Nicole caused approximately $1 billion in damage, according to NOAA, and five fatalities. It was only the third November hurricane to make landfall in Florida.  

Ian (2022): The strongest hurricane of the 2022 season, Ian was a Category 5 storm at peak intensity with sustained winds of 160 mph and a minimum central air pressure of 937 mb. It made landfall in southwest Florida on September 28 as a Category 4 storm with sustained winds of 150 mph and caused widespread damage. It made a secondary landfall as a Category 1 storm in South Carolina on September 30. It was responsible for over 150 fatalities and is the third costliest hurricane in U.S. history having caused $118.5 billion in damages (2024 dollars).

Unforgettable September storms

 

Hurricane Florence, September 2018 (Source: NOAA)

The Mid-Atlantic Region is no stranger to the devastation of tropical storms. September hurricanes or their remnants have brought extraordinary weather to the DMV in recent decades.

2018: A Cape Verde hurricane that lasted more than two weeks, Hurricane Florence was a Category 4 storm at peak intensity over the Atlantic Ocean with sustained winds of 150 mph.  Fortunately, it weakened to Category 1 intensity (90 mph winds) before its September 14 landfall in North Carolina.  Since the atmospheric steering currents were weak, it meandered across the Carolinas and Mid-Atlantic Region for several days. Its remnants caused devastating flooding and severe weather, including a rainfall record of 2.22” at BWI Airport on September 18.  

2004: Hurricane Ivan made landfall as a Category 3 (120 mph winds) on the U.S. Gulf Coast on September 16. It had far-reaching impacts and its remnants sparked a tornado outbreak on September 17, 2004 in the Mid-Atlantic Region. 

Ivan was the top tornado producing hurricane, on record, with a total of 127 tornadoes in the United States, according to NOAA. Also, Dulles Airport had a September 17 rainfall record of 1.71” from Ivan’s remnants.  

2003: Hurricane Isabel reached peak intensity as a Category 5 over the open Atlantic with sustained winds of 165 mph.  Fortunately, Isabel weakened to a Category 2 storm before its September 18 landfall in North Carolina.  Isabel tracked west of Washington, D.C. and brought heavy rain and gusty winds. There were over one million power outages around the nation’s capital, with significant coastal flooding in Alexandria, Virginia and Annapolis, Maryland.    

The highest tide in Annapolis reached 7.58 feet above normal, breaking the 1933 hurricane record.  Flooding in Georgetown occurred with flood stage reaching 11.3 feet above normal, which broke the 1933 hurricane surge record. Also, daily rainfall records occurred at DC’s three area airports on September 18.

1999: As a borderline Category 4/5 hurricane with peak sustained winds of 155 mph, Hurricane Floyd was the most intense hurricane of the 1999 season. Floyd weakened to a Category 2 hurricane with sustained winds of 105 mph before its September 16 landfall near Cape Fear, North Carolina.  

As Floyd continued its trek northward, it brought flooding rainfall, damaging winds and coastal flooding.  Widespread flooding occurred in the D.C. Metro Region. Floyd’s September 16 rainfall records include 2.05” at Dulles Airport and 5.02” at BWI Airport.